Quiz #4 - Chapter 4 - Variability Flashcards
A researcher summarized the descriptive statistics for pain scores in her study comparing a new pain medication (treatment group) to a placebo (control group). A higher score in her questionnaire reflects a higher level of pain. The results indicate that the sample mean of the treatment group was 80 and the sample standard deviation was 10. The sample mean of the control group was 75 and the sample standard deviation was 12. In which group are pain scores most similar to one another?
A: Control group
B: Treatment group
B: Treatment group
In a normal distribution with a mean of 60 and a standard deviation of 10, which of the following interpretations is definitely true?
A: All scores are within ± 10 points from the mean
B: 95% of scores are within ± 20 points from the mean
C: All scores are within ± 20 points from the mean
D: The average squared difference between a score and the mean is 10 points
E: The difference between the lowest and highest score is 20
F: 68% of scores are within ± 10 points from the mean
B: 95% of scores are within ± 20 points from the mean AND
F: 68% of scores are within ± 10 points from the mean
A researcher is summarizing a sample of ages and reports that the average difference between a respondent’s age and the sample mean is 8 years. Which measure of variability is she reporting?
A: Deviation score
B: Standard deviation
C: Sum of squares
D: Variance
B: Standard deviation
A researcher summarizes a sample of income scores and reports that the average squared difference between a respondent’s income and the sample mean is 10,000. Which measure of variability are they reporting?
A: Deviation score
B: Sum of squares
C: Standard deviation
D: Variance
D: Variance
The population standard deviation formula has N in the denominator, whereas the sample standard deviation formula has N-1 in the denominator. What is the rationale for using N-1 rather than N?
A: Dividing by N would make the sample standard deviation a more accurate estimate of the population standard deviation
B: We don’t know the population mean and hence use the sample mean as a replacement. As a consequence, the sum of squares tends to be too small. N-1 is used to counteract the effect from the small sum of squares.
C: We don’t know the number of observations in the full population, so we use N-1 as an estimate of the number of observations
B: We don’t know the population mean and hence use the sample mean as a replacement. As a consequence, the sum of squares tends to be too small. N-1 is used to counteract the effect from the small sum of squares.
If a participant in a study obtained a score of 90 but the mean is 100, then what is the deviation score for this participant?
-10
__________ describes the relation between sample mean and the population mean, as __________ describes the relation between individual score and sample mean (or
population mean).
A: Standard deviation, variance
B: Standard deviation, sampling error
C: Variance, standard deviation
D: Sampling error, standard deviation
D: Sampling error, standard deviation
As sample size increases, sampling error generally:
A: Decreases
B: Stays the same
C: Increases
D: We don’t know
A: Decreases
A researcher calculates the standard deviation of salaries and obtains a value of zero. Which of the following is true?
A: All salaries were identical
B: A mistake was made, the standard deviation cannot equal zero
C: Salaries were normally distributed around the mean
A: All salaries were identical
When we calculate a sample standard deviation, we divide by N-1, not N. What would happen if we divided by N instead?
A: The parameter would be too small
B: The parameter would be too large
C: The estimate would be too small
D: The estimate would be too large
C: The estimate would be too small
Please see Google Doc for additional questions with graphs and images!
Please see Google Doc for additional questions with graphs and images!
