Stats Final

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

+1.50

Which of the following Pearson correlations shows the greatest strength or consistency of relationship?

-0.90

A normal distribution has m = 20 and s = 4. What is the probability of randomly selecting a score greater than 25 from this distribution?

.1065

A sample of n = 9 individuals is selected from a population with m = 60 and ơ= 6, and a treatment is administered to the sample. After treatment, the sample mean is M = 63. What is the value of Cohen's d for this sample?

.67

A vertical line drawn through a normal distribution at z = 0.50 separates the distribution into two sections, the body and the tail. What proportion of the distribution is in the body?

.6915

What proportion of a normal distribution is located between z = -1.25 and z = +1.25?

.7888

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

0

A random sample of n = 9 scores is selected from a normal distribution with m = 80 and s = 12. What is the probability that the sample mean will be between 76 and 84?

0.6426

A repeated-measures study comparing two treatments with a sample of n = 4 participants produces a mean of M = 18 with SS = 24 for the scores in the first treatment, a mean of M = 14 with SS = 18 for the scores in the second treatment, and a mean of MD = 4 with SS = 12 for the difference scores. What is the estimated standard error for the sample mean difference?

1

What is the value of 𝛴(X - 1)^2 for the scores 1, 2, 1, 4?

10

What is the value of 𝛴(X - 2 )^2 for the scores 2, 3, 5?

10

A class consists of 10 males and 30 females. A random sample of n = 3 students is selected. If the first two students are both females, what is the probability that the third student is a male?

10/40

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 F-ratio with df = 1, 24 for an independent-measures experiment. If all the treatments had the same number of participants, then how many individuals were in each treatment?

13

A population of N = 10 scores has a mean of m = 6. After one score is removed, the mean is found to be M = 5. What is the value of the score that was removed?

15

A population of N = 100 scores has m = 30 and s = 4. What is the population variance?

16

A sample of n = 25 scores has a mean of M = 40 and a standard deviation of s = 10. What is the estimated standard error for the sample mean?

2

A sample of n = 9 scores has a variance of s2 = 36. What is the estimated standard error for the sample mean?

2

2 treatments with n=4, mD =2, SS=75. What is the standard error of the sample mean difference?

2.5

A researcher reports t(22) = 5.30, p < .01 for an independent-measures experiment. How many individuals participated in the entire experiment?

24

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

3

For an independent-measures ANOVA comparing three treatments with a sample of n = 5 in each treatment, what is the critical value for the F-ratio using a = .05?

3.88

A sample obtained from a population with s = 12 has a standard error of 2 points. How many scores are in the sample?

36

A sample of n = 4 scores is selected from a population with m = 40 with s = 8, and the sample mean is M = 43. What is the standard error for the sample mean?

4

For a sample with M = 80, a score of X = 88 corresponds to z = 2.00. What is the sample standard deviation?

4

Two samples, each with n = 5 scores, have a pooled variance of 40. What is the estimated standard error for the sample mean difference?

4

For the following distribution of quiz scores, if a score of X = 3 or higher is needed for a passing grade, how many individuals failed the quiz?

5

A researcher would like to test the claim that 9 out of 10 doctors prefer Brand X. A sample of 60 doctors is obtained and each is asked to compare Brand X with another leading brand. The data show that 48 of the doctors picked Brand X. If these data are evaluated using a chi-square test for goodness of fit, what is the expected frequency for Brand X?

54

Samples of size n = 9 are selected from a population with m = 80 with s = 18. What is the standard error for the distribution of sample means?

6

If random samples, each with n = 9 scores, are selected from a normal population with m = 80 and s = 18, how much difference, on average, should there be between a sample mean and the population mean?

6 points

A population of N = 7 scores has a mean of m = 10. If one score with a value of X = 4 is removed from the population, what is the value for the new mean?

66/6=11

For the regression equation Y = X - 2, if the mean for Y is MY = 6, what is the mean for X?

8

A treatment is administered to a sample of n = 9 individuals selected from a population with a mean of m = 80 and a standard deviation of s = 12. After treatment, the effect size is measured by computing Cohen's d, and a value of d = 0.50 is obtained. Based on this information, what is the mean for the treated sample?

86

A set of n = 4 scores has a mean of m = 11. If 8 points are subtracted from one of the scores, what is the new value for the population mean?

9

What is the value of SS for the following set of scores? Scores: 1, 1, 4, 0

9

A researcher measures IQ and weight for a group of college students. What kind of correlation is likely to be obtained for these two variables?

A correlation near zero

For an ANOVA comparing three treatment conditions, what is stated by the alternative hypothesis (H1)?

At least one of the three population means is different from another mean.

In an analysis of variance, differences caused by treatment effects contribute to which of the following variances?

Between-treatments variance but not within-treatments variance

Which of the following will increase the power of a statistical test?

Change the sample size from n = 25 to n = 100

Which of the following research situations would be most likely to use an independent-measures design?

Compare the mathematics skills for 9th-grade boys versus 9th-grade girls

For which of the following situations would a repeated-measures research design be appropriate?

Comparing pain tolerance with and without acupuncture needles

What kind of variable requires the use of real limits?

Continuous

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

Even if a treatment has an effect, it is still possible to obtain a sample mean that is very similar to the original population mean. What outcome is likely if this happens?

Fail to reject H0 and make a Type II error

A research report describing the results from a repeated-measures t test states that "t(22) = 1.71, p > .05." From this report, what was the outcome of the hypothesis test?

Fail to reject the null hypothesis with a sample of n = 23 participants

Which of the following is an accurate definition of a Type II error?

Failing to reject a false null hypothesis

The data for a chi-square test consist of ___________.

Frequency counts and nominal categories

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

If the sample size (n) is very large

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

If the sample statistic is equal to the corresponding population parameter, then the statistic is unbiased.

For the independent-measures t statistic, what is the effect of increasing the difference between sample means?

Increase the likelihood for rejecting H0 and increase measures of effect size

Which of the following accurately describes the effect of increasing the alpha level?

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

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

Interval or ratio

How does sample variance influence the estimated standard error and measures of effect size such as r2 and Cohen's d?

Larger variance increases the standard error but decreases measures of effect size.

For a normal population with m = 40 and s = 10, which of the following samples has the highest probability of being obtained?

M<42 for a sample of n=4

What is the preferred measure of central tendency for scores measured on an ordinal scale?

Median

The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores?

Negatively skewed

Which of the following accurately describes the chi-square distribution?

Positively skewed with all values greater than or equal to zero

What values are specified by the null hypothesis for the chi-square test for goodness of fit?

Proportions for the entire population

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

R=-.70

What kind of measurement scale is necessary to conclude that one score is twice a big as another?

Ratio

In an analysis of variance, which of the following is determined by the size of the sample variances?

SSwithin

For the regression equation, = -2X + 6, what can be determined about the correlation between X and Y?

The correlation definition will be negative

A random sample of n = 60 scores is selected from a population. Which of the following distributions definitely will be normal?

The distribution of sample means will form a normal distribution.

What happens to the shape of the chi-square distribution as the df value increases?

The mode (highest point) of the distribution moves to the right.

A researcher obtains a negative value for chi-square statistic. What can you conclude because the value is negative?

The researcher made a mistake; the value of Chi-squared cannot be negative

A researcher selects a sample and administers a treatment to the individuals in the sample. If the sample is used for a hypothesis test, what does the null hypothesis (H0) say about the treatment?

The treatment has no effect on the scores

If other factors are held constant, which of the following sets of data would produce the largest value for an independent-measures t statistic?

The two samples both have n = 30, with sample variances of 20 and 25.

Which of the following is not needed to compute a t statistic?

The value of the population variance or standard deviation

For an ANOVA comparing three treatment conditions, what is stated by the null hypothesis (H0)?

There are no differences between any of the population means

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

There is little or no effect on measures of effect size, but the likelihood of rejecting the null hypothesis increases.

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

You complete a hypothesis test using a = .05, and based on the evidence from the sample, your decision is to reject the null hypothesis. If the treatment actually has no effect, which of the following is true?

You might have made a Type I error, but the probability is less than 5%

One sample of n = 8 scores has a variance of s2 = 6 and a second sample of n = 8 scores has s2 = 10. If the pooled variance is computed for these two samples, then the value obtained will be ______.

exactly halfway between 6 and 10

Samples of n = 16 scores are selected from a population. If the distribution of sample means has an expected value of 40 and a standard error of 2, what are the mean and the standard deviation for the population?

m = 40 and ơ=8

A sample is selected from a population with m = 70, and a treatment is administered to the sample. After treatment, the sample mean is M = 74, and Cohen's d is d = 1.00. What is the value of the sample variance?

s^2 = 16

A researcher selects a sample and administers a treatment to the individuals in the sample. If the sample is used for a hypothesis test, what does the alternative hypothesis (H1) say about the treatment?

the treatment causes a change in the scores

If a sample of n = 4 scores is obtained from a population with m = 70 and s = 12, what is the z-score corresponding to a sample mean of M = 73?

z = 0.50

A random sample of n = 4 scores is obtained from a population with a mean of m = 80 and a standard deviation of s = 10. If the sample mean is M = 90, what is the z-score for the sample mean?

z=2.00

A sample of n = 9 scores has a variance of s2 = 18. If the scores were a population, what value would be obtained for the population variance.

ơ^2 = 16