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A consumer advocate was interested in the effectiveness of Evelyn Wood’s Speed-Reading Course.  One hundred students were randomly sampled from a population of college sophomores.  Two groups of fifty students were created using random assignment.  Group A (treatment) received the course while Group B (control) was instructed to use whatever means necessary to improve reading speed and comprehension.  After the course, a reading achievement test was given to the students in each group (higher test scores indicate higher levels of speed and comprehension), and the results were as follows: Group A (Treatment) Group B (Control) n 50 50 Mean 75 80 SD 23 20 On the basis of these results, which of the following is the most reasonable conclusion?

For a population with a given proportion, p, how would the standard error of the sampling distribution of the proportion change if the sample size is increased by a factor of 4, from 400 to 1600.

A 98% confidence interval for the proportion of hotel reservations that are canceled on the intended arrival day is (0.048 , 0.112).  What is the value of the standard error used to construct this interval?

Diet soda does not taste as good as regular soda, but there is a question as to whether diet soda has fewer calories than regular soda.  To examine this question, a nutritionist obtained recently produced 12-ounce samples of regular and diet soda.  He determined the number of calories in each 12-ounce sample and obtained the following summary statistics: Regular Soda Diet Soda n 64 64 Mean 125 115 SD 16 20 What is the appropriate standard error for testing the null hypothesis that the population mean difference is zero?

A survey is planned, to estimate the percent of U.S. shoppers who pay with credit cards.  Prior surveys suggest that 54% of all U.S. shoppers pay with credit cards.  What is the minimum number of randomly selected shoppers we must survey in order to obtain a 95% confidence interval with a margin of error no bigger than 0.01?

In a recent study of perfect pitch, 141 UI music students were randomly sampled.  Of 46 males, 14 had perfect pitch, whereas 38 out of 95 females had perfect pitch.  Which of the following gives a 98% confidence interval for the difference in population proportions between male and female music students at UI?

A consumer advocate was interested in the effectiveness of Evelyn Wood’s Speed-Reading Course.  One hundred students were randomly sampled from a population of college sophomores.  Two groups of fifty students were created using random assignment.  Group A (treatment) received the course while Group B (control) was instructed to use whatever means necessary to improve reading speed and comprehension.  After the course, a reading achievement test was given to the students in each group (higher test scores indicate higher levels of speed and comprehension), and the results were as follows: Group A (Treatment) Group B (Control) n 50 50 Mean 75 80 SD 23 20 Suppose the observed P-value for testing the null hypothesis that the population mean difference is zero was 0.06 (it isn’t).  That means that

Which focal length gives a wider angle of view? ©

Two methods of teaching statistics are to be compared.  Method A (traditional) involves lectures, textbook, and study manuals.  Method B (experimental) involves the use of computerized instruction, with each student using the computer whenever s/he pleases for as long as s/he pleases.  From the 32 students who enrolled for this course, one-half were randomly assigned to each method.  At the end of the semester, a valid achievement test was given to the students in both groups.  The results of this study will be used to help decide if Method B should be adopted in place of Method A.  The following summary statistics were obtained: Method A Method B n 16 16 Mean 50 57 SD 10 10 The researcher decided to construct a two-sided 90% confidence interval for the population mean difference.  Assuming the estimated standard error was 3.0 (actually it was not) and using the sample data provided, which of the following represents the appropriate interval?

What two things can be used to increase or decrease the amount of light that enters a camera? ©