Statistics

My electric bills for June, July, and August last summer were $75, $75, and $150, respectively. What was the mean amount for the three bills?

$100

For a population with m = 70 and s = 8, what is the z-score corresponding to X = 82?

+1.50

A population has SS = 100 and s2 = 4. What is the value of S(X - m) for the population?

0

A random sample of n = 9 scores is obtained from a normal population with m = 40 and s = 18. What is the probability that the sample mean will be greater than M = 43?

0.3085

A set of n = 25 pairs of scores (X and Y values) has a Pearson correlation of r = 0.80. How much of the variance for the Y scores is predicted by the relationship with X?

0.64 or 64%

A normal distribution has a mean of m = 70 with s = 12. If one score is randomly selected from this distribution, what is the probability that the score will be greater than X = 58?

0.8413

For a repeated-measures study comparing two treatments with a sample of n = 9 participants, the difference scores have a mean of MD = 4.90 with SS = 72. What is the estimated standard error for the sample mean difference?

1

What is the mode for the following sample of n = 8 scores? Scores: 0, 1, 1, 1, 2, 2, 3, 3

1

A repeated-measures experiment and a matched-subjects experiment each produce a t statistic with df = 10. How many individuals participated in each study?

11 for repeated and 22 for matched

A researcher reports an independent-measures t statistic with df = 16. How many participants were in the entire study?

17

A repeated-measures study using a sample of n = 20 participants would produce a t statistic with df = ____.

19

Two samples each have n = 4 scores. If the first sample has a variance of 10 and the second sample has a variance of 6, what is the estimated standard error for the sample mean difference?

2

A repeated-measures study comparing two treatments with a sample of n = 4 participants produces MD = 3 with SS = 48 for the set of difference scores. What is the repeated-measures t statistic for these data?

3/2 = 1.50

For a sample of n = 30 scores, a score that is 6 points above the mean has a z-score of z = 1.50. What is the sample standard deviation?

4

What is the mean for the following sample of scores? Scores: 1, 4, 5, 6

4

A sample of n = 6 scores has a standard deviation of s = 3. What is the value of SS, the sum of the squared deviations for this sample?

45

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

47

The following data were obtained from a repeated-measures research study. What is the value of SS for the difference scores? Subject 1st 2nd #1 10 11 #2 4 6 #3 7 9 #4 6 5

6

A set of n = 15 pairs of scores (X and Y values) has SSX = 4, SSY = 25, and SP = 6. What is the Pearson correlation for these data?

6/10

The data from an independent-measures research study produce a sample mean difference of 6 points and an estimated standard error of 2 points. If there are n = 8 scores in each sample, what is the value for the t statistic?

6/2

For the following distribution, how many people have scores greater than X = 14?

7

Two samples, each with n = 16 scores, produce an estimated standard error of 4 points and a t statistic of t = 2.00. What is the sample mean difference?

8

One sample with n = 4 scores has a mean of M = 12, and a second sample with n = 6 scores has a mean of M = 8. If the two samples are combined, what is the mean for the combined set of scores?

9.6

A biologist records the number of trout, bass, perch, and other types of fish caught in a local lake during a 2-week period. If the results are organized in a frequency distribution graph, what kind of graph should be used?

A bar graph

Which set of sample characteristics is most likely to produce a significant value for the independent-measures t statistic and a large measure of effect size?

A large mean difference and small sample variances

A sample is selected from a population with a mean of m = 40. If the sample mean is M = 45, which of the following combinations would make the sample mean an extreme, unrepresentative value for the population?

A large sample and a small population standard deviation

If other factors are held constant, how does sample size influence the likelihood of rejecting the null hypothesis and measures of effect size such as r2 and Cohen's d?

A larger sample increases the likelihood but has little influence on measures of effect size.

A researcher surveys a sample of n = 200 college students and asks each person to identify his or her favorite movie from the past year. If the data were organized in a frequency distribution table, what would be listed in the first column?

A list of movies

A researcher plans to conduct a research study comparing two treatment conditions with a total of 20 participants. Which of the following designs would produce 20 scores in each treatment?

A repeated-measures design

What is the effect of decreasing the alpha level (for example, from a = .05 to a = .01)?

All of the other options are results of decreasing alpha.

What is the relationship between the alpha level, the size of the critical region, and the risk of a Type I error?

As the alpha level increases, the size of the critical region increases, and the risk of a Type I error increases.

With a = .05, how are the boundaries for the critical region determined?

Boundaries are drawn so there is 2.5% (.025) in each tail of the distribution.

For any distribution, what is the z-score corresponding to the median?

Cannot be determined from the information given

Which of the following accurately describes the effect of increasing the sample size?

Decreases the standard error and has no effect on the risk of a Type I error

A biologist records the number of trout, bass, perch, and other types of fish caught in a local lake during a 2-week period. If the results are organized in a frequency distribution table, what values would be listed in the first column?

Different types of fish

The scatter plot for a set of X and Y values shows the data points clustered in a nearly perfect circle. For these data, what is the most likely value for the Pearson correlation?

Either positive or negative near 0

Under what circumstances can a very small treatment effect be statistically significant?

If the sample size big and the sample variance is small

Which of the following would have no effect on the width of a confidence interval?

Increase the sample mean

For statistical purposes, it usually is not important to differentiate between which two scales of measurement?

Interval and ratio

A sample has a mean of M = 39.5 and a standard deviation of s = 4.3, and produces a t statistic of t = 2.14. For a two-tailed hypothesis test with a = .05, what is the correct statistical decision for this sample?

It is impossible to make a decision about H0 without more information.

What happens to the expected value of M as sample size increases?

It stays constant.

Which of the following describes what a confidence interval does?

It uses a sample mean to estimate the corresponding population mean.

Which combination of factors is most likely to produce a significant value for an independent-measures t statistic?

Large samples and small variance

A sample of n = 4 scores is obtained from a population with m = 70 and s = 8. If the sample mean corresponds to a z-score of 2.00, what is the value of the sample mean?

M = 78

One sample is selected to represent scores in treatment 1 and a second sample is used to represent scores in treatment 2. Which set of sample statistics would present the clearest picture of a real difference between the two treatments?

M1 = 36, M2 = 40, and both variances = 6

For a repeated-measures study comparing two treatment conditions, a researcher obtains Cohen's d = 0.50 for a sample of n = 4 scores with a variance of s2 = 16. What is the value of the sample mean?

MD = 2

If a set of scores is displayed in a frequency distribution bar graph, what scale of measurement was used to measure the scores?

Nominal or ordinal

A researcher takes a sample from a population and computes a statistic for the sample. Which of the following statements is correct?

None of the other statements is correct.

In a repeated-measures experiment, each individual participates in one treatment condition and then moves on to a second treatment condition. One of the major concerns in this type of study is that participation in the first treatment may influence the participant's score in the second treatment. What is this problem is called?

Order effects

Which correlation should be used to measure the relationship between gender and grade point average for a group of college students?

Point-biserial correlation

What would the scatter plot show for data that produce a Pearson correlation of r = +0.88?

Points clustered close to a line that slopes up to the right

If a hypothesis test produces a z-score in the critical region, what decision should be made?

Reject the null hypothesis

A hypothesis test involves a comparison of which two elements?

Research results from a sample and a hypothesis about a population

A researcher conducts a hypothesis test to evaluate the effect of a treatment. The hypothesis test produces a z-score of z = 2.37. Assuming that the researcher is using a two-tailed test, what decision should be made?

The researcher should reject the null hypothesis with a = .05 but not with a = .01.

A researcher expects a treatment to increase the scores for individuals in a population. The treatment is evaluated using a one-tailed hypothesis test, and the test produces z = +2.40. Based on this result, what is the correct statistical decision?

The researcher should reject the null hypothesis with either a = .05 or a = .01

Which of the following possibilities is a serious concern with a repeated-measures study?

The results will be influenced by order effects.

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.

With a = .05 and df = 8, the critical values for a two-tailed t test are t = ±2.306. Assuming all other factors are held constant, if the df value were increased to df = 20, what would happen to the critical values for t?

They would decrease (move closer to zero).

When is there a risk of a Type I error?

Whenever H0 is rejected

A researcher predicts that scores in treatment A will be higher than scores in treatment B. If the mean for the 10 participants in treatment A is 4 points higher than the mean for the 10 participants in treatment B and the data produce t = 2.095, what decision should be made?

With a = .05, reject H0 for a one-tailed test but fail to reject for a two-tailed test

A normal distribution has a mean of m = 24 with s = 3. What is the minimum score needed to be in the top 14% of the distribution?

X = 27.24

A distribution with m = 55 and s = 6 is being standardized so that the new mean and standard deviation will be m = 50 and s = 10. When the distribution is standardized, what value will be obtained for a score of X = 58 from the original distribution?

X = 55

If there is a positive correlation between X and Y, then the regression equation Y = bX + a will have _____.

b > 0

A researcher uses a repeated-measures study to compare two treatment conditions with a set of 20 scores in each treatment. What would be the value of df for the repeated-measures t statistic?

df = 19

After measuring two individuals, a researcher can say that Tom's score is 4 points higher than Bill's. The measurements must come from a(n) _______ scale.

interval or ratio

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

m = 48

Which of the following is the correct null hypothesis for an independent-measures t test?

m1 - m2 = 0

Using letter grades (A, B, C, D, and E) to classify student performance on an exam is an example of measurement on a(n) _______ scale of measurement.

ordinal

A random sample of n = 16 scores is selected from a normal distribution with m = 500 and s = 200. For this sample, which of the following is true?

p(402 < M < 598) = 0.95

A researcher is curious about the average monthly cell phone bill for high school students in the state of Florida. If this average could be obtained, it would be an example of a ______.

parameter

For which of the following Pearson correlations would the data points be clustered most closely around a straight line?

r = -0.70

A researcher administers a treatment to a sample of participants selected from a population with m = 80. If the researcher obtains a sample mean of M = 88, which combination of factors is most likely to result in rejecting the null hypothesis?

s = 5 and a = .05

What is the sample variance and the estimated standard error for a sample of n = 9 scores with SS = 72?

s2 = 9 and sM = 1

What z-score value separates the highest 70% of the scores in a normal distribution from the lowest 30%?

z = -0.52