Social Stat Exam 2

When conducting hypothesis tests for two sample means, the term μ1 - μ2 in the numerator of the formula reduces to zero because A. the standard deviations are calculated first. B. the tests are conducted at very low alpha levels. C. the samples are independent as well as random. D. the null hypothesis is assumed to be true.

D. the null hypothesis is assumed to be true.

When testing for the significance of the difference between two sample means, the null hypothesis is that A. the sample standard deviations are different. B. the sample means are different. C. the populations from which the sample was drawn are different. D. the populations from which the sample was drawn are the same.

D. the populations from which the sample was drawn are the same.

With alpha set at .05, the Critical Region for a two-tailed test would begin at ± 1.96. In a one-tailed test at the same alpha level the Critical Region would begin at A. ± 1.96. B. ± 2.58. C. ± 2.30. D. ± 1.65.

D. ± 1.65.

According to the text, on the issue of abortion, A. Democratic and Republican opinion has grown increasingly alike over the years. B. Democratic and Republican opinion has grown increasingly apart over the years. C. Democratic women have become increasingly like Republican women. D. Young Democrats and young Republicans have become increasingly alike.

B. Democratic and Republican opinion has grown increasingly apart over the years.

Which of the following is NOT an assumption required for a test of hypothesis with a single sample mean? A. A representative sample B. Sample size (N) larger than 1,000 C. Normal sampling distribution D. Interval-ratio level of measurement

B. Sample size (N) larger than 1,000

From a University population, random samples of 45 seniors and 37 freshmen have been given a scale that measures sexual experiences. The freshmen report an average of 1.6 sexual partners over their lifetimes while seniors report an average of 2.5 partners. The t (obtained) for this difference was -3.56 while the t (critical) was ± 2.34. What can be concluded? A. There is no significant difference between the classes. B. Seniors and freshman are significantly different in their sexual experiences. C. Freshmen are more sexually active. D. Sexual mores are deteriorating.

B. Seniors and freshman are significantly different in their sexual experiences.

A researcher is interested in the effect that neighborhood crime-watch efforts have on the crime rate in the inner city, but he is unwilling to predict the direction of the difference. The appropriate test of hypothesis would be A. one-tailed. B. two-tailed. C. descriptive. D. symmetrical.

B. two-tailed.

The shape of the sampling distribution of sample means can be assumed to be normal when N is A. a large percentage of the population. B. any number as long as you know the value of the population mean. C. 100 or more. D. at least twice the value of the population standard deviation.

C. 100 or more.

The average weight of a sample of women who attend aerobics classes at the YWCA is 130 pounds. We construct a confidence interval (using an alpha of 0.05) of ± 3.45. The upper and lower limits of our estimate are A. 130.00 and 133.45. B. 126.55 and 130.45. C. 126.55 and 133.45. D. unknown; these values will depend on the number of women who are truly serious about exercising.

C. 126.55 and 133.45.

Sixty percent of the respondents in a random sample drawn from a neighborhood are Democrats. The community as a whole is 75% Democrat. The difference between sample and population has been tested and the null hypothesis has been rejected. What may we conclude? A. Type I error has been committed. b. A one-tailed test has been used. C. The neighborhood is significantly less likely to be Democrat. D. The difference is not significant.

C. The neighborhood is significantly less likely to be Democrat.

Which of the following was true for the test for differences in average income by gender reported in the text? A. The information on income came from the U.S. Bureau of the Census. B. The income of males, on the average, was almost twice that of females. C. The test compared only people who worked full time. D. The test compared only people who had a least a high school education.

C. The test compared only people who worked full time.

A researcher questioned 45 randomly-selected members of the freshman class about their experiences drinking alcohol and used these responses to estimate the drinking behavior of the entire freshman class of 1500. In this example, the 45 interviewees were the __________ and the ___________ was the population. A. sample, student body B. parameters, freshman class C. statistics, parameters D. sample, freshman class

D. Sample, freshmen class

Under what condition might we use proportions rather than means as the test statistic? A. When sample size is very small B. When sample size is very large C. When the variable of interest is only interval-ratio in level of measurement D. When the variable of interest is only nominal in level of measurement

D. When the variable of interest is only nominal in level of measurement.

When a list of the population does not exist, the probability sampling technique most commonly used is A. simple random. B. stratified. C. systematic. D. cluster.

D. cluster

The t distribution, compared to the Z distribution, is A. more skewed. B. more peaked for small C. samples but increasingly like the Z distribution as N increases. bimodal. D. flatter for small sample sizes but increasingly like the Z distribution as N increases.

D. flatter for small sample sizes but increasingly like the Z distribution as N increases.

For a simple random sample, each case and each combination of cases in the population must A. be representative. B. be included in the sample. C. be contacted by the researcher. D. have an equal probability of being chosen for the sample.

D. have an equal probability of being chosen for the sample.

The more efficient the estimate, the more the sampling distribution A. is evenly spread from the mean to ± 2 standard deviations. B. becomes flatter. C. clusters to the right of the mean. D. is clustered around the mean.

D. is clustered around the mean.

Samples are to populations as A. big to little B. central tendency is to dispersion. C. measures are to variables. D. statistics are to parameters.

D. statistics are to parameters

A major limitation for stratified sampling is that A. the samples so selected are not representative. B. it violates the rule of EPSEM. C. the samples are non-random. D. the exact composition of the population is usually unknown.

D. the exact composition of the population is usually unknown.

​To calculate degrees of freedom, a researcher uses which formula?

df = N-1

In terms of Z scores, the absolute value of the critical value for a one-tailed test is​ ​A. less than it is for a two-tailed test. ​B. greater than it is for a one-tailed test. ​C. greater for lower tails than upper tails. ​D. greater for upper tails than lower tails.

​A. less than it is for a two-tailed test.

In terms of hypothesis testing, "significance" refers to the​ A. difference between an independent and dependent variable. ​B. difference between the sample and population values. C. ​difference between the two independent variables. D. ​difference between our observed and our predicted outcomes.

​B. difference between the sample and population values.

A pooled estimate A. compares two different populations. ​B. combines two different populations. ​C. combines information from two samples. ​D. is the mean of two standard deviations.

​C. combines information from two samples.

To calculate the confidence interval based on sample means, you need all but which of the following​ ​A. sample mean. ​B. Z score determined by alpha level. ​C. standard error of the mean. ​D. standard deviation of the population.

​D. standard deviation of the population.

The fundamental principle of probability sampling is that a sample selected by________ is very likely to be __________. A. EPSEM, representative B. stratification, large C. telephone polls, cheap D. clusters, stratified

A. EPSEM, representative

When testing for the significance of the difference between a sample mean and a population mean, degrees of freedom are equal to A. N - 1 B. N + 1 C. alpha. D. 1 - alpha.

A. N - 1

From a University population, random samples of 145 men and 237 women have been asked if they have ever cheated in a college class. 8% of the men and 6% of the women said that they have. What is the appropriate test to assess the significance of this difference? A. Test for the significance of the difference between two sample proportions, large samples. B. Test for the significance of the difference between two sample proportions, small samples. C. Test for the significance of the difference between two sample proportions, matched samples. D. Test for the significance of the difference between two sample proportions, large samples.

A. Test for the significance of the difference between two sample proportions, large samples.

When testing for the significance of the difference between two sample means, which parameters must be estimated with sample values? A. The population standard deviations B. The population means C. The standard deviation of the sampling distribution D. The alpha value

A. The population standard deviations

The higher the alpha level, the more likely we will A. commit a Type I error. B. commit a Type II error. C. conduct a two-tailed test. D. be unable to decide whether to reject or fail to reject the null hypothesis.

A. commit a Type I error.

The research and null hypotheses _________ each other. A. contradict B. complement C. amplify D. rescind

A. contradict

The research hypothesis (H1) typically states what the researcher expects to find and A. contradicts the null hypothesis. B. verifies the null hypothesis. C. modifies the null hypothesis. D. is unrelated to the null hypothesis.

A. contradicts the null hypothesis.

In a one-tailed test of hypothesis, the entire _________ should be placed in either the upper or lower tail of the ____________. A. critical area, sampling distribution B. sample mean, population distribution C. Z score, critical area D. sampling distribution, sample distribution

A. critical area, sampling distribution

Two sample statistics are unbiased estimators. They are A. means and proportions. B. means and standard deviations. C. medians and modes. D. proportions and percentages.

A. means and proportions.

Samples from two high schools are being tested for the difference in their average levels of prejudice. One sample contains 39 respondents and the other sample contains 47 respondents. The appropriate sampling distribution is the A. t distribution. B. Z distribution. C. F distribution. D. Any of the above

A. t distribution

The lower the alpha level, A. the lower the probability of rejecting the null hypothesis. B. the larger the sample size has to be to reject the null hypothesis. C. the greater the probability of rejecting the null hypothesis. D. the more desirable the two-tailed test.

A. the lower the probability of rejecting the null hypothesis.

If we reject a null hypothesis of "no difference" at the 0.05 level A. the odds are 20 to 1 in our favor that we have made a correct decision. B. the null hypothesis is true. C. the odds are 5 to 1 in our favor that we have made a correct decision. D. the research hypothesis is true.

A. the odds are 20 to 1 in our favor that we have made a correct decision.

When using sample means as estimators, we usually estimate the population standard deviation with A. the sample standard deviation. B. the sampling distribution standard deviation. C. the population parameter. D. the Z score.

A. the sample standard deviation.

When testing for the significance of the difference between two sample means, we must first estimate ___________ before we can compute the test statistic. A. the standard deviation of the sampling distribution B. the standard deviations of the samples C. the population means D. the critical region

A. the standard deviation of the sampling distribution

When testing a single sample mean for significance when the population standard deviation is unknown and sample size is 75, the correct sampling distribution is A. the t distribution. B. the Z distribution. C. it makes no difference. D. t for a one-tailed test, Z for a two-tailed test.

A. the t distribution.

The text reports the results of a test for the significance of the difference in average education for random samples of males and females. Males averaged 13.76 years of schooling and females averaged 14.04 years. The Z score computed in step 4 for this difference was - 1.49. Given these results, which of the following is a reasonable conclusion? A. The difference is statistically significant, large, and important. B. The difference is not statistically significant and was probably caused by random chance. C. There is an important gender gap in education in the United States. D. This difference is statistically significant but quite small.

B. The difference is not statistically significant and was probably caused by random chance.

Which of the following must be normally distributed in order to proceed with hypothesis testing of means and proportions? A. The sample distribution B. The sampling distribution C. The population distribution D. Both the sample distribution and the population distribution

B. The sampling distribution

Based on an EPSEM sample of 300 state university students, we estimate that the average number of hours of study time each week is 30 ± 2. In this example, the population is A. the 300 state university students. B. all state university students. C. unknown. D. the same as the parameter.

B. all state university students.

The probability that an interval estimate does not include the population value is called A. the margin. B. alpha. C. an error. D. the odds.

B. alpha.

Since critical values of t vary by sample size, before using the t table we must first calculate A. the Z score. B. degrees of freedom. C. the population standard deviation. D. the alpha level.

B. degrees of freedom.

If the test statistic does not fall in the critical region, we A. reject the null hypothesis. B. fail to reject the null hypothesis. C. lower the alpha level and conduct a new test. D. commit a Type I error.

B. fail to reject the null hypothesis.

Sample size and the width of confidence intervals A. increase at the same rate. B. increase at different rates: sample size increases faster than interval width. C. increase at different rates: sample size increases more slowly than interval width. D. have no relationship to each other.

B. increase at different rates: sample size increases faster than interval width.

As our confidence in an interval estimate increases, the width of the interval A. decreases. B. increases. C. remains the same. D. increases or decreases depending on the alpha level.

B. increases.

When random samples are drawn so that the selection of a case for one sample has no effect on the selection of cases for another sample, the samples are A. dependent. B. independent. C. simple. D. systematic.

B. independent.

To satisfy the requirement of independent random sampling, the researcher A. must use only cluster sampling. B. may randomly select cases from one list of the population, then subdivide that sample according to the trait of interest. C. may randomly select an entire neighborhood, then select any member of each family in that neighborhood. D. must select only very small populations.

B. may randomly select cases from one list of the population, then subdivide that sample according to the trait of interest.

The larger the sample size, the A. more important the observed difference. B. more likely we are to reject the null hypothesis. C. less likely we are to reject the null hypothesis. D. lower the Z score.

B. more likely we are to reject the null hypothesis.

In estimation procedures, as the alpha level decreases, the corresponding Z score A. moves closer to the mean of the sampling distribution. B. moves away from the mean of the sampling distribution. C. becomes negative. D. becomes positive.

B. moves away from the mean of the sampling distribution.

In order to reject the null hypothesis when using the t distribution and small samples, we will A. need a smaller test statistic as compared to larger samples. B. need a larger test statistic as compared to larger samples. C. always use one-tailed tests. D. set alpha very low.

B. need a larger test statistic as compared to larger samples.

When testing for the significance of the difference between two samples, the null hypothesis states that the ____________ are the same. A. sample means B. population means C. sampling distributions D. population standard deviations

B. population means

To increase the probability that a confidence interval will include the population parameter A. lower the alpha level. B. raise the alpha level. C. increase the bias of the sample statistic. D. set efficiency to zero.

B. raise the alpha level.

Which of the following is necessary to calculate the standard error of the mean?​ ​A. variance. ​B. standard deviation of the population. C. ​correlation between population and sample. D. ​median of the population.

B. standard deviation of the population.

In tests of significance, if the test statistic falls in the critical region, we may conclude that A. the population distribution is normal. B. the null hypothesis can be rejected. C. the research hypothesis is true. D. our sample size was too small.

B. the null hypothesis can be rejected.

According to the theorems presented in Chapter 6, we can be sure that the sampling distribution is normal if A. the population is small. B. the population is normal. C. the sample is stratified. D. the sample is normal.

B. the population is normal.

When solving the formula for finding Z(obtained) with sample proportions in the two-sample case, we must first estimate A. the standard deviation of the population. B. the population proportion. C. the ratio of the sample proportions. D. the critical region.

B. the population proportion.

Unlike the sample and population distributions, the sampling distribution is A. empirical. B. theoretical. C. random. D. EPSEM.

B. theoretical

In comparing a sampling distribution with a population distribution, A. There will always be more variance in the sampling distribution. B. there will always be more variance in the population distribution. C. as the size of the sample increases the two distributions will become identical. D. the two distributions will always be the same.

B. there will always be more variance in the population distribution.

The records of the state Division of Motor Vehicles reveals that 23% of all drivers have been ticketed at least once. Twenty five percent of a random sample of older drivers in the state have gotten at least one ticket. This difference has been tested and the researcher has failed to reject the null hypothesis. What can be concluded? A. Older drivers are better drivers. B. Older drivers are worse drivers. C. There is no significant difference between older drivers and drivers in general in terms of number of tickets. D. Older drivers are significantly different from drivers in general.

C. There is no significant difference between older drivers and drivers in general in terms of number of tickets.

For testing the difference between two sample means, the level of measurement is assumed to be A. nominal. B. ordinal. C. interval-ratio. D. Any of the above

C. interval-ratio.

When we decide on a value for alpha, we are A. defining the likelihood of accepting the alternative hypothesis. B. establishing whether the test will be one or two tailed. C. setting the probability of committing a Type I error. D. setting the probability of a one-tailed test.

C. setting the probability of committing a Type I error.

The probability of Type I error is A. .01 B. .05 C. the alpha level. D. beta.

C. the alpha level.

For tests of significance involving two sample proportions, the value of the population proportion is estimated from A. the value of the sample means. B. the value of Z (obtained). C. the sample proportions. D. the sample standard deviations.

C. the sample proportions.

The standard error of the mean is the same thing as A. the standard deviation of a sample. B. the standard deviation of a population. C. the standard deviation of a sampling distribution. D. the variance of a sample.

C. the standard deviation of a sampling distribution.

All other things being equal, with which of the following alpha levels would we be most likely to reject the null hypothesis? A. .01 B. .001 C. .05 D. .10

D. .10

For all tests of hypothesis, the probability of rejecting the null hypothesis is a function of A. the size of the observed differences. B. the alpha level and the use of one- or two-tailed tests. C. sample size. D. All of the above

D. All of the above

The width of an interval estimate can be controlled by A. changing the confidence level. B. changing the alpha level. C. changing the sample size. D. Any of the above

D. Any of the above