Section 3 PSYC 311

A sample of n = 20 scores is transformed into z-scores. What is the mean for the set of 20 z-scores?

0

A sample of n = 4 scores has SS = 48. What is the estimated standard error for the sample mean?

2

A sample of scores has M = 80. In this sample, a score of X = 86 corresponds to z = +2.00. What is the sample standard deviation?

3

For a sample with M = 50 and s = 12, what is the X-value corresponding to z = -0.25?

47

A summary value, usually numerical, that describes a sample is called a parameter.

False

In a distribution with M = 80 and s = 20, a score of X = 95 corresponds to z = 1.50.

False

If other factors are held constant, what is the effect of increasing the sample size?

It will decrease the estimated standard error and increase the likelihood of rejecting the null hypothesis.

A sample with M = 85 and s = 12 is transformed into z-scores. After the transformation, what are the values for the mean and standard deviation for the sample of z-scores?

M=0 and s=1

In a sample with s = 8, a score of X = 44 corresponds to a z-score of z = -0.50. What is the sample mean?

M=48

Why are t statistics more variable than z-scores?

The extra variability is caused by variations in the sample variance.

Which of the following is a fundamental difference between the t statistic and a z-score?

The t statistic uses the sample variance in place of the population variance.

If other factors are held constant, as the sample size increases, the estimated standard error decreases.

True

If other factors are held constant, as the sample variance increases, the estimated standard error also increases.

True

On an exam, Tom scored 12 points above the mean and had a z-score of +2.00. The standard deviation for the set of exam scores must be 6.

True

Transforming an entire distribution of scores into z-scores will not change the shape of the distribution.

True

The ages of the children in a summer camp range from 7 to 12 years old. A counselor constructs a frequency distribution graph showing the number of children for each of the six age groups. Which of the following graph would be most appropriate for this distribution?

a histogram

Statistical techniques that summarize, organize, and simplify data are best classified as ____ statistics.

descriptive

In n = 25 games last season, the college basketball team averaged M = 76 points with a standard deviation of s = 6. In their final game of the season, the team scored 89 points. Based on this information, the number of points scored in the final game was _____

far above average

When n is small (less than 30), how does the shape of the t distribution compare to the normal distribution?

it is flatter and more spread out than the normal distribution

For scores measured on a nominal scale of measurement (for example, job classification), which measure of central tendency is appropriate?

mode

Which of the following samples will have the smallest value for the estimated standard error?

n=100 with s=10

A sample of n = 16 scores produces a one-sample t-statistic = 2. 00. If the sample is used to measure effect size with r2, what value will be obtained for r2?

r2 = 4/19

On an exam with M = 52, you have a score of X = 56. Which value for the standard deviation would give you the highest position in the class distribution relative to the rest of the students?

s=2

On an exam with M = 52, you have a score of X = 44. Which value for the standard deviation would give you the highest position in the class distribution relative to the rest of the students?

s=8

The most commonly used descriptive statistics for a set of numerical scores are the mean and the ____.

standard deviation

A researcher records the change in weight (gain or loss) during the first semester of college for each individual in a group of 25 freshmen, and calculates the average change in weight. The average is an example of a ____.

statistic

A researcher uses an anonymous survey to investigate the study habits of American college students. Based on the set of 56 surveys that were completed and returned, the researcher finds that these students spend an average of 4.1 hours each week working on course material outside of class. For this study, the average of 4.1 hours is an example of a(n) ____.

statistic

A researcher has measured self-esteem for a sample of 40 first-grade children. The researcher would like to divide the children into two equal-sized groups consisting of the high self-esteem kids and the low self-esteem kids. Which statistical measure will identify the correct score to serve as the boundary between the high and the low self-esteem groups?

the median

Two samples from the same population both have n = 10 scores with M = 45. If the t statistic is computed for each sample, then what is the relationship between the two t values?

the sample with the smaller variance will produce the larger t statistic

Under what circumstances is a score that is 15 points above the mean an extreme score relatively far from the mean?

when the population standard deviation is much smaller than 15