Research Methods final exam

The critical value of χ 2 ( χ 2 crit)

increases as we increase the degrees of freedom

The ___________ of an estimate is determined by the level of confidence

certainty

When we reject the null hypothesis in the analysis of variance we can conclude that

at least one of the means is different from at least one other mean.

The chi-square test is used when we have

categorical data

Calculate the lower and upper limits of the 90% confidence interval for a sample of n = 17 with a mean M = 18.43 and standard error of the mean sM = .72. Assume it is a two-tailed distribution.

(17.17, 19.69)

. A researcher compares differences in response to shock among rats given an electric stimulation of 1, 3, and 5 volts. If she observes 20 rats in each group, then what are the degrees of freedom for the one-way between-subjects ANOVA?

(2,57)

​ Which of the following describes a typical distribution of F-ratios?

. ​Positively skewed with all values greater than or equal to zero

​ In an ANOVA, what is represented by the letter N?

. ​The total number of scores in the entire study

If we run six independent comparisons among means, each at the five percent level, the overall familywise error rate will be approximately

.30

A cellphone company wants to compare cellphone applications to send text messages. The company test the first application, which allows the participants (n D = 121) to delete their contents. If the sample mean difference is M D = 200, and the estimated standard error for the difference scores, s MD = 25. Estimate the 95% confidence interval for these data? Assuming a two-tailed distribution, what is lower confidence interval? Enter the numerical value below. Include one digit after the decimal point.

150.5

A researcher selects a sample of 80 people and records the frequency of participants choosing a low, moderate, or high calorie dessert in a buffet. What are the degrees of freedom for this chi-square goodness-of-fit test?

2

​ For an independent-measures ANOVA comparing three treatments with a sample of n = 5 in each treatment, what is the critical value ( Fcrit ) using α = .05?

3.88

​ Ten years ago, only 20% of the U.S. population consisted of people more than 65 years old. A researcher plans to use a sample of n = 200 people to determine whether the population distribution has changed during the past ten years. If a chi-square test is used to evaluate the data, what is the expected frequency for the older-than-65 category?

40

A researcher compares the frequency of participants who sleep primarily on their stomach, back, or side during the night. What is the critical value (χ2crit) for a chi-square goodness-of-fit test at a .05 level of significance?

5.99

A researcher records the frequency of participants selecting one of four new slogans for an advertising campaign. If it was expected that among 200 people polled there would be no preference for any one slogan, then what was the expected frequency for each slogan.

50 people

"Elementary school children spent significantly more time reading when their teacher was present than when the teacher was absent, t(7) = 2.804, p < .05 (d2 = 0.46)." In this related samples t test, how many participants were observed?

8

Which of the following confidence intervals has the most precision?

80% confidence interval

A researcher conducts a chi-square goodness-of-fit test in which k = 5. What is the critical value for this test at a .05 level of significance?

9.49

Calculate the 90% confidence interval for a sample of N = 25 with a mean M = 2.75 and standard error of the mean sM = .19.

90% CI = 2.75 ± .33

Calculate the 90% confidence interval for a sample of n = 12 with a mean M = 4 and standard error of the mean sM = .58. Assume it is a two-tailed distribution.

90% CI = 4.00 ± 1.04

Calculate the 95% confidence interval for a sample with a mean M = 117.52 and a population standard error of the mean σM = 5.57. Assume a two-tailed distribution.

95% CI = 117.52 ± 10.92

Calculate the 99% confidence interval for a sample of n = 19 with a mean M = 27.18 and standard error of the mean sM = 2.37.

99% CI = 27.18 ± 6.82

If a researcher wants a wider confidence interval, which of the following would be calculated?

99% confidence interval

Which of the following confidence intervals has the least precision?

99% confidence interval

What is the general formula to find the confidence interval of the mean of population?

CI population mean = point estimate ± Interval estimate

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

Comparing pain tolerance of a group with and without acupuncture needles

Which of the following is an assumption about nonparametric tests?

Data from a sample is being used to estimate the population parameter.

______ is the probability of making at least one type I error across a set of comparisons.

Familywise error

A research company would like to determine the effectiveness of a pain-relief ointment designed for lower back pain. Prior to testing the ointment, each of the patients fill out a survey to rate their current level of back pain on a scale from 1 to 10. Then, they apply the ointment and after 90 minutes of the application, they fill out the survey a second time. The data are show in the table. If a two-tailed related samples t statistic at the .05 level of significance is computed, what is the null and the alternative hypothesis?

H0: μD = 0 (there is no difference in pain rating before and after applying the pain-relief ointment); H1: μD ≠ 0 (there is a difference between the pain rating before and after applying the pain-relief ointment)

Which of the following was NOT an advantage of repeated measures designs?

It is easier to calculate the statistics.

​ 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

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

Positively skewed with all values greater than or equal to zero

How does the calculation for a t using the repeated measures versus the matched samples design differ?

The calculation of the related samples t statistic for the repeated measures and the matched samples designs do not differ; the test statistic is computed the same.

​ How does the difference between f e and f o influence the outcome of a chi-square test?

The larger the difference, the larger the value of chi-square and the greater the likelihood of rejecting the null hypothesis.

​ When comparing more than two treatment means, why should you use an analysis of variance instead of using multiple t tests?

Using multiple t tests increases the risk of a Type I error.

If we compute a ANOVA and determine we should reject the null hypothesis ( H0), what do we need to do to find out which groups are different?

We need to compute a pairwise comparison or a posthoc test.

A confidence interval is ______.

a range or interval of values that has a stated probability of containing an unknown population parameter

A point estimate is ______.

a single value used to estimate an unknown population parameter

A researcher conducts a chi-square goodness-of-fit test in which k = 3 and χ2obt = 4.32. What is the decision for this test at a .05 level of significance?

accept the null hypothesis

Which of the following tests measure the size of the discrepancy between an observed and expected frequency at each level of a categorical variable?

chi-square goodness of fit test

A professor computes the mean difference in exam scores before and after a lecture as 9.0±14.5 (), and this difference was significant. What is the effect size for this result using estimated Cohen's d?

d = 0.62 (medium effect)

When a researcher increases the confidence level from 95% to 99%, the wider interval implies ______.

decreased precision in estimating the population mean

The ______ of the Fobt or F-ratio represents the ______ variability, which may also be thought of as ______.

denominator; within-group; 'error'

When we speak about "error variance" in the analysis of variance we are speaking of

differences of subjects in the same group.

You are interested in know how many red m&m's you have in a bag that is supposed to have 10. You count the number of m&m's and you find there are 8 red m&m's. In this example, the 10 m&m's represent _________ and the 8 represent _________.

expected frequency (fe); observed frequency (fo)

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

frequencies

Arnie is working on his RMI homework. He is asked to compare the means of three groups and calculated a value of -2.01 for the F-ratio (Fobt). This implies _____

he has made an error in his calculations... he is working with variances, which are always positive.

The degrees of freedom for a chi-square goodness-of-fit test are

k - 1

A researcher asks a sample of brothers and sisters to rate how positive their family environment was during childhood. In this study, the differences in ratings between each brother and sister pair were compared. The type of design described here is called a

matched-samples design

Which of the following is a type of related samples design in which different participants are actually observed in each group, but treated statistically as if they are the same persons in each group.

matched-samples design

Nonparametric statistical tests are used in research situations in which the dependent variable is measured at which levels of measurement?

nominal

An important assumption in the one-way analysis of variance is that

observations are independent

The ____________ of an estimate is determined by the range of the confidence interval

precision

A researcher compares the difference in the number of text messages sent by students in a class during the first week and then during the last week of classes. The type of design described here is called a

repeated-measures design

Knowing the range of the confidence interval is important because the ________ the range, the ___________ precise the estimate.

smaller; more

If a researcher chooses the 99% confidence interval instead of the 95% confidence interval, how does it affect the value of tcrit ?

tcrit is higher.

Cohen's d refers to

the difference between the means before and after treatment divided by a standard deviation.

Keeping in mind the general formula of the confindence interval, what is the relationship between the size of a sample and the width of the confidence interval for the mean?

the larger the sample size, the narrower the confidence interval for the mean.

In the analysis of variance with three groups the null hypothesis is

the three population means are equal to each other.

The analysis of variance compares

the variance between group means with the variance within groups.

A goodness-of-fit test is

used to test the null hypothesis that the data are distributed in a way that would be predicted by previous research, or a theory.

When drawing a conclusion about the 95% confidence interval with a known population standard deviation, a researcher would state that there is a _____

we are 95% confident that the interval contains the true mean of the population.

When a researcher moves from a 95% confidence level to a 99% confidence level, the confidence interval for the mean becomes ______.

wider

Which of the following is the correct null hypothesis for a repeated-measures t test?

µD = 0