STAT 219 | Week 18 Quiz | Complete Solution

Does taking Vitamin D increase the mean lifespan of a rat? A sample of 20 rats was randomized to group 1 (control) and group 2 (Vitamin D). The lifespan (days) of each rat was measured. Here is some of the output:    Which of the following is correct?   
(a) About 95% of the time the lifespan increases by 80 days.  
(b) If we were to repeat the experiment many times, then the confidence interval will contain the population value about 95% of the time.  
(c) There is about a 3% chance that the lifetimes are longer for group 2.  
(d) The standard deviation of the increase in lifetime is about 40 days. 


Does taking Vitamin D increase the mean lifespan of a rat? A sample of 20 rats was randomized to group 1 (control) and group 2 (Vitamin D). The lifespan (days) of each rat was measured. Here is some of the output:    Which of the following is correct?   
(a)     (b)     (c)     (d)   
 
Does taking Vitamin D increase the mean lifespan of a rat? A sample of 20 rats was randomized to group 1 (control) and group 2 (Vitamin D). The lifespan (days) of each rat was measured. Here is some of the output:    Which of the following is correct?   
(a) Because 10 rats were randomized to each of the two groups, a matched pairs design could be used.  
(b) About 95% of rats in group 1 have lifetimes between 470 days and 590 days.  
(c) Because the two standard deviations are about equal, there is no evidence that the average lifetimes are different.  
(d) The standard errors measure how much the average lifetime for each group could

 
Which of the following would lead us to believe that the t procedures were not safe to use in a two-sample problem with 100 subjects in each group?   
(a) The same medians and means for the two groups were slightly different.  
(b) The distribution of the data values were moderately skewed.  
(c) The data was only integers so cannot be Normally distributed.  
(d) Several outliers were detected in each group.

Which of the following is correct?   
(a) Two-sample procedures should be used with matched pairs designs.  
(b) If some of the matched pairs are missing some data, use a two-sample procedure as it does not require equal sample size in each group.  
(c) The sample sizes in each group need to be equal to use two-sample procedures.  
(d) Two-sample procedures can be used with random samples from each group and for experiments where a single population is randomized to the two groups. 
 


IQ tests were administered to 31 seventh-grade girls and 47 seventh-grade
boys in a Midwest school district. The following is the output from an analysis of the data:   Which of the following is correct?  
 (a) The two histograms are not identical. Therefore there is good evidence that the mean IQ scores differ between males and females.  
(b) We are 95% confident that each boy has an IQ score that is 5 points greater than their matched girl.   (c) Because the 95% confidence interval contains the value 0, there is no evidence of a difference in mean IQ score.  
(d) The standard error measures the variation in IQ scores in each group. 


 
IQ tests were administered to 31 seventh-grade girls and 47 seventh-grade boys in a Midwest school district. The following is the output from an analysis of the data:    Which of the following is correct for testing the hypothesis of equality of mean IQ scores versus a difference in either direction?   
(a)     (b)     (c)     (d)   


 
IQ tests were administered to 31 seventh-grade girls and 47 seventh-grade boys in a Midwest school district. The following is the output from an analysis of the data:    Which of the following is correct?   
(a) There is a 0.11 chance that the mean IQ scores differ between males and females.  
(b) The probability that there is no difference in mean IQ scores is 0.11.  
(c) Because the p-value is 0.11, there is no evidence ( ) of a difference in mean IQ scores between males and females.  
(d) Because the p-value is 0.11, there is evidence ( ) of a difference in mean IQ scores between males and females.


Different varieties of the tropical flower Heliconia are fertilized by different species of hummingbirds. Over time, the lengths of the flowers and the forms of the hummingbirds' beaks have evolved to match each other. The following is an analysis of the length (mm) of the two color varieties:    Which of the following is correct to examine if the mean length differs between the two varieties?   
(a)     (b)     (c)     (d)   


 
Different varieties of the tropical flower Heliconia are fertilized by different species of hummingbirds. Over time, the lengths of the flowers and the forms of the hummingbirds' beaks have evolved to match each other. The following is an analysis of the length (mm) of the two color varieties:    Which of the following is correct?  
(a) The estimated difference in mean length between the two varieties is 3.53 (SE 0.45) mm. Because the confidence interval does not contain 0, there is evidence of a difference in mean length.  
(b) About 95% of flowers have a difference in lengths between 2.6 and 4.4 mm.  
(c) The dot-plot shows several outliers. Consequently, the t procedure is invalid. 
(d) The degrees of freedom are fractions but the t table shows that they are integers. An error must have been made in computing the degrees of freedom.