Statistics How To

Different Sampling Methods: What’s the Difference?

Main Index> Basic Statistics>Different Sampling Methods

 

Different Sampling Methods: What’s the Difference: Overview

different sampling methods

You’ll come across many terms in statistics that define different sampling methods: simple random sampling, systematic sampling, stratified samples and cluster samples. You can find a run down on the different types of sampling techniques here. It can be overwhelming to learn all these new terms and to try and remember what each one of the different sampling methods means. Luckily, their names give away their meaning and (unlike many things in statistics!), it’s a straightforward process to figure out what kind of sample you have.

Different Sampling Methods: What’s the Difference: Steps

Step 1: Find out if the study sampled from individuals (for example, picked from a pool of people). You’ll find random sampling in a school lottery, where individual names are picked out of a hat. But a more “systematic” way of choosing people can be found in “systematic sampling,” where every nth individual is chosen from a population. For example, every 100th customer at a certain store might receive a “doorbuster” gift.

Step 2: Find out if the study picked groups of participants. For large numbers of people (like the number of potential draftees in the Vietnam war), it’s much simpler to pick people by groups (simple random sampling). In the case of the draft, draftees were chosen by birth date, “simplifying” the procedure.

Step 3: Determine if your study contained data from more than one carefully defined group (“strata” or “cluster”). Some examples of strata could be: Democrats and Republics, Renters and Homeowners, Country Folk vs. City Dwellers, Jacksonville Jaguars fans and San Francisco 49ers fans. If there are two very distinct, clear groups, you have a stratified sample or a “cluster sample.” If you have data about the individuals in the groups, that’s a stratified sample. In order to perform stratified sampling on this sample, you could perform random sampling of each strata independently. If you only have data about the groups themselves (you may only know the location of the individuals), then that’s a cluster sample.

Step 4: Find out if the sample was easy to get. Convenience samples are like convenience stores: why go out of your way to get samples, when you can nip out to the corner store? A classic example of convenience sampling is standing at a shopping mall, asking passers by for their opinion.

6 thoughts on “Different Sampling Methods: What’s the Difference?

  1. Sandy

    Can you please help provide answers to these questions on statistics? I need to know how they got the answers.
    Thank you.
    Question 1
    A sample of serum cholesterol levels of six men who visited a cholesterol screening clinic located in your city yielded values of

    218, 273, 210, 259, 290, 232

    The mean cholesterol level in this sample is
    Answer

    229.5

    245.5

    *247.0

    266.0
    Question 2
    A researcher wants to determine how many individuals have health insurance. They decide to do a telephone survey using a list of telephone numbers that are subdivided into zip codes. It is determined that a representative sample from each zip code will be drawn. This type of sampling is:
    Answer

    cluster sampling.

    systematic sampling.

    stratified random sampling.

    convenience sampling.
    Question 3
    What type of sampling is usually the easiest to do?
    Answer

    Quota sampling

    Simple random sampling

    * Convenience sampling

    Cluster sampling

    Question 4
    All human blood can be typed as one of O, A, B, or AB. The distribution of the types varies a bit with race. Choose an African American at random. Here are the approximate probabilities that the person you choose will have blood type O, B, or AB.

    Blood Type O A B AB
    Probability 0.50 ? 0.20 0.05

    The probability that the person chosen has blood type A is:
    Answer

    0.04

    *0.25

    0.27

    0.95
    Question 5
    Which of the following variables is an example of the nominal level of measurement?
    Answer

    Rank in graduating class

    Letter grade (i.e. A, B, C, D, or F)

    Age of students

    Amount of money earned
    Question 6
    Which variable would be considered to be measured at the ordinal level?
    Answer

    Religious affiliation

    SAT score

    Temperature

    Severity of pain scale
    Question 7
    The characteristics of the normal distribution curve include the following except:
    Answer

    The total area under the curve represents 100% of all values.

    The mean and median are found below the apex.

    5% of the values lie beyond 2 standard deviations from the median.

    The curve is not symmetrical.

    All of the above.

    Question 8
    The ratio level of measurement would include which of the following?
    Answer

    Systolic blood pressure

    Order of finishing test

    Political affiliation

    GRE score

    Question 9
    A scattergram can be used to display:
    Answer

    correlation.

    causality.

    nominal data.

    categorical data.
    Question 10
    In a set of scores with a mean of 100 and a standard deviation of 15, what raw score is represented by a z score of 1.00?
    Answer

    115

    130

    100

    70
    Question 11
    What is the median of 2, 2, 2, 3, 3, 5, 5, 6, 6,7?
    Answer

    5.5

    6

    4

    41

    Question 12
    What is the range of 2, 12, 1, 10, and 22?
    Answer

    48

    6

    10

    21
    Question 13
    How can descriptive statistics be defined?
    Answer

    Descriptive statistics describe the general characteristics of a distribution.

    Descriptive statistics relate the data to a larger population.

    Descriptive statistics develop the research question.

    Descriptive statistics are identical to inferential statistics.
    Question 14
    In a normal distribution, what percentage of scores fall between the mean and a z score of +1.00?
    Answer

    16%

    34%

    50%

    95%

    Question 15
    When a researcher draws conclusions about a population based on the results of a test on a sample, he or she is most likely using which of the following?
    Answer

    Inductive statistics

    Deductive statistics

    Descriptive statistics

    Inferential statistics
    Question 16
    What can you conclude if the obtained value of a test statistic exceeds the critical value?
    Answer

    The null hypothesis cannot be rejected.

    You made an error when calculating the test statistic.

    The null hypothesis can be rejected.

    Your obtained value is not statistically significant.

    Question 17
    Which is the strongest correlation?
    Answer

    + 0.76

    + 0.21

    – 0.01

    – 0.88
    Question 18
    If you calculated a correlation coefficient of .35, how would you describe this value?
    Answer

    Moderate

    Weak

    Very strong

    Very weak

    Question 19
    Emergency room physicians at four hospitals (who serve very different median income geographic areas) hypothesized that children who arrive at the emergency room after swallowing objects are at increased risk of elevated blood lead levels. Four groups of thirty-five children each are selected from each hospital who presented with foreign bodies in their gastrointestinal tract were screened for blood lead levels. The mean was 15.7 ug/dL for group 1, 14 ug/dL for group 2, 10 ug/dL for group 3, and 20 ug/dL for group 4. They believe that there will be a significant difference among groups. The best statistical test to use for this study is the:
    Answer

    ANOVA test.

    Chi-square test.

    student t-test.

    regression analysis test.
    Question 20
    The county health department in your geographic area would like to know how many children who live in the county are being immunized by doctors or by the county health department. A comparison is wanted of children younger than 2 years of age who use the county health department services with those who don’t. A county health survey is conducted, which interviewed a random sample of 42,000 children younger than 2 years of age. The population of the survey would be:
    Answer

    the 42,000 children younger than 2 years of age in your county.

    all people who use health services in your county.

    all people who do not use health services in your area county.

    all children younger than 2 years of age in your county.
    Question 21
    In 10 randomly sampled children referred for recurrent episodes of ear aches the mean number of times the children went swimming in a week was 10 times. Assume the swimming data is normally distributed. What type of statistical test would be best to use in this situation to determine if there is a difference in the mean number of times children went swimming between the healthy population and the 10 randomly sampled children?
    Answer

    Student’s t-test

    ANOVA test

    Chi-square test

    Regression test
    Question 22
    Studying the association between blood cholesterol levels and changes in blood pressure, a researcher would obtain the most effective use of the data by the application of:
    Answer

    student’s t-test.

    f-test.

    Chi-square test.

    analysis of variance.

    correlation analysis.
    Question 23
    The correlation between the age and height of children is found to be about r = y of the child. We conclude:
    Answer

    the least squares regression line of y on x would have a slope of 0.7.

    the fraction of the variation in heights explained by the least squares regression line of y on x is 0.49.

    about 70% of the time, age will accurately predict height.

    height is generally 70% of child’s age.
    Question 24
    To assess the possible association between tobacco use and the subsequent development of lung cancer, a total of 135 patients were studied. The results were as follows:

    Lung Cancer (+) No Lung Cancer (-) Total
    Used Tobacco (+) 36 31 67
    Did Not Use Tobacco (-)22 46 68
    Total 58 77 135

    The most appropriate test to use in comparing the proportion of cancer patients who used tobacco to those who did not and subsequent development of lung cancer is:
    Answer

    Chi-square test.

    ANOVA test.

    t-test.

    correlation test.
    Question 25
    In a study at a school, the mean systolic blood pressure of 250 medical students was 116 mm Hg, with a standard deviation of 4 mm Hg. From the data, 99.7% of the medical students will have systolic blood pressures (mm Hg) in the range of:
    Answer

    110-130

    104-128

    112-120

    116-124

  2. Andale

    Sandy,

    Thanks for stopping by. My work schedule doesn’t give me the time, unfortunately, to answer stats questions in comments. you can try posting in our forums (click the tab at the top) but you may want to start with one or two questions as out mods work for free ;)

    Regards,
    Stephanie

  3. Jamie Johns

    Can you please help provide answers to these questions on statistics? I need to know how they got the answers.
    Thank you.
    Question 1
    A sample of serum cholesterol levels of six men who visited a cholesterol screening clinic located in your city yielded values of
    218, 273, 210, 259, 290, 232
    The mean cholesterol level in this sample is
    Answer
    229.5
    245.5
    *247.0**
    266.0
    Question 2
    A researcher wants to determine how many individuals have health insurance. They decide to do a telephone survey using a list of telephone numbers that are subdivided into zip codes. It is determined that a representative sample from each zip code will be drawn. This type of sampling is:
    Answer
    cluster sampling.
    systematic sampling.
    stratified random sampling.***
    convenience sampling.
    Question 3
    What type of sampling is usually the easiest to do?
    Answer
    Quota sampling
    Simple random sampling
    * Convenience sampling****
    Cluster sampling
    Question 4
    All human blood can be typed as one of O, A, B, or AB. The distribution of the types varies a bit with race. Choose an African American at random. Here are the approximate probabilities that the person you choose will have blood type O, B, or AB.
    Blood Type O A B AB
    Probability 0.50 ? 0.20 0.05
    The probability that the person chosen has blood type A is:
    Answer
    0.04
    *0.25***
    0.27
    0.95
    Question 5
    Which of the following variables is an example of the nominal level of measurement?
    Answer
    Rank in graduating class
    Letter grade (i.e. A, B, C, D, or F)****
    Age of students
    Amount of money earned
    Question 6
    Which variable would be considered to be measured at the ordinal level?
    Answer
    Religious affiliation
    SAT score
    Temperature
    Severity of pain scale****
    Question 7
    The characteristics of the normal distribution curve include the following except:
    Answer
    The total area under the curve represents 100% of all values.
    The mean and median are found below the apex.
    5% of the values lie beyond 2 standard deviations from the median.
    The curve is not symmetrical.****
    All of the above.
    Question 8
    The ratio level of measurement would include which of the following?
    Answer
    Systolic blood pressure***
    Order of finishing test
    Political affiliation
    GRE score
    Question 9
    A scattergram can be used to display:
    Answer
    correlation.***
    causality.
    nominal data.
    categorical data.
    Question 10
    In a set of scores with a mean of 100 and a standard deviation of 15, what raw score is represented by a z score of 1.00?
    Answer
    115***
    130
    100
    70
    Question 11
    What is the median of 2, 2, 2, 3, 3, 5, 5, 6, 6,7?
    Answer
    5.5
    6
    4**
    41
    Question 12
    What is the range of 2, 12, 1, 10, and 22?
    Answer
    48
    6
    10
    21**
    Question 13
    How can descriptive statistics be defined?
    Answer
    Descriptive statistics describe the general characteristics of a distribution.***
    Descriptive statistics relate the data to a larger population.
    Descriptive statistics develop the research question.
    Descriptive statistics are identical to inferential statistics.
    Question 14
    In a normal distribution, what percentage of scores fall between the mean and a z score of +1.00?
    Answer
    16%
    34%***
    50%
    95%
    Question 15
    When a researcher draws conclusions about a population based on the results of a test on a sample, he or she is most likely using which of the following?
    Answer
    Inductive statistics
    Deductive statistics
    Descriptive statistics
    Inferential statistics****
    Question 16
    What can you conclude if the obtained value of a test statistic exceeds the critical value?
    Answer
    The null hypothesis cannot be rejected.
    You made an error when calculating the test statistic.
    The null hypothesis can be rejected.***
    Your obtained value is not statistically significant.
    Question 17
    Which is the strongest correlation?
    Answer
    + 0.76
    + 0.21
    – 0.01
    – 0.88**
    Question 18
    If you calculated a correlation coefficient of .35, how would you describe this value?
    Answer
    Moderate***
    Weak
    Very strong
    Very weak
    Question 19
    Emergency room physicians at four hospitals (who serve very different median income geographic areas) hypothesized that children who arrive at the emergency room after swallowing objects are at increased risk of elevated blood lead levels. Four groups of thirty-five children each are selected from each hospital who presented with foreign bodies in their gastrointestinal tract were screened for blood lead levels. The mean was 15.7 ug/dL for group 1, 14 ug/dL for group 2, 10 ug/dL for group 3, and 20 ug/dL for group 4. They believe that there will be a significant difference among groups. The best statistical test to use for this study is the:
    Answer
    ANOVA test.***
    Chi-square test.
    student t-test.
    regression analysis test.
    Question 20
    The county health department in your geographic area would like to know how many children who live in the county are being immunized by doctors or by the county health department. A comparison is wanted of children younger than 2 years of age who use the county health department services with those who don’t. A county health survey is conducted, which interviewed a random sample of 42,000 children younger than 2 years of age. The population of the survey would be:
    Answer
    the 42,000 children younger than 2 years of age in your county.
    all people who use health services in your county.
    all people who do not use health services in your area county.
    all children younger than 2 years of age in your county.****
    Question 21
    In 10 randomly sampled children referred for recurrent episodes of ear aches the mean number of times the children went swimming in a week was 10 times. Assume the swimming data is normally distributed. What type of statistical test would be best to use in this situation to determine if there is a difference in the mean number of times children went swimming between the healthy population and the 10 randomly sampled children?
    Answer
    Student’s t-test***
    ANOVA test
    Chi-square test
    Regression test
    Question 22
    Studying the association between blood cholesterol levels and changes in blood pressure, a researcher would obtain the most effective use of the data by the application of:
    Answer
    student’s t-test.
    f-test.
    Chi-square test.
    analysis of variance.
    correlation analysis.
    Question 23
    The correlation between the age and height of children is found to be about r = y of the child. We conclude:
    Answer
    the least squares regression line of y on x would have a slope of 0.7.
    the fraction of the variation in heights explained by the least squares regression line of y on x is 0.49.****
    about 70% of the time, age will accurately predict height.
    height is generally 70% of child’s age.
    Question 24
    To assess the possible association between tobacco use and the subsequent development of lung cancer, a total of 135 patients were studied. The results were as follows:
    Lung Cancer (+) No Lung Cancer (-) Total
    Used Tobacco (+) 36 31 67
    Did Not Use Tobacco (-)22 46 68
    Total 58 77 135
    The most appropriate test to use in comparing the proportion of cancer patients who used tobacco to those who did not and subsequent development of lung cancer is:
    Answer
    Chi-square test.
    ANOVA test.
    t-test.
    correlation test.
    Question 25
    In a study at a school, the mean systolic blood pressure of 250 medical students was 116 mm Hg, with a standard deviation of 4 mm Hg. From the data, 99.7% of the medical students will have systolic blood pressures (mm Hg) in the range of:
    Answer
    110-130
    104-128****
    112-120
    116-124

  4. Andale

    Unfortunately, time constraints prevent me from answering stats related questions on the comments section. But please ask for help on our forums — one of our moderators will be glad to help! (By the way, you’ll be more likely to get a response on the forums if you ask one question at a time :) )

    http://www.statisticshowto.com/forums/

  5. Tiffany

    A principal told his faculty that the ABC test, the PALS test, and the Sesame Street test could be used to predict whether or not a student passed their 3rd grade Reading SOL test. When one of the teachers asked him how he knew this, he said that he read an article that showed that the reliability of those three tests on the 3rd grade Reading SOL test was α =.437. Was he correct? Explain.