Researchers were interested in the effect of sleep on memory consolidation. Twenty-four participants were randomly assigned to either a “Sleep” or “No-Sleep” group, such that there were 12 participants in each group. On the first day, all participants were flashed pictures of 15 different objects on a computer screen and asked to remember as many objects as possible. That night, the “Sleep” group got an ordinary night’s sleep. The “No-Sleep” group was kept awake until the second night. All participants got an ordinary night’s sleep on the second and third nights. On the fourth day, all participants were tested to see how many of the original 15 objects they remembered. The data is below. Conduct an independent samples t-test, two-tailed, alpha = .05. Sleep NoSleep 14 8 13 9 8 6 9 13 11 7 10 9 9 10 13 12 12 8 11 11 14 9 13 12  Write the null hypothesis in symbols and words. Write the alternative hypothesis in symbols and words. By hand, calculate the degrees of freedom. Show calculation. Use software to obtain the test statistic and p-value. Make a decision about the null using the p-value approach. Write the conclusion in APA style Compute and report the 95% CI. Interpret the 95% CI. Using the CI, make a decision about the null hypothesis. Be sure to explain your reasoning. Does this agree with your decision from part (2)?

A research study was conducted to examine the clinical efficacy of a new drug used to improve memory. Students were randomly assigned to one of four groups: a placebo group, a group that received a low dose of the drug, and a group that received a moderate dose of the drug, and a group that did not receive any dose. Students were administered their respective doses and had to study for a Spanish vocabulary test. The group who did not receive any drug, was just told to study for the test. None of the 31 students spoke Spanish. Below is an ANOVA table used to analyse the results from the test: Source SS df MS F Between XX XX XX XX Within XX ? XX Total What is the missing value for the degrees of freedom for the "within" row (marked by a ?)? Answer:

A psychology lab doing research in dreams has 4 rooms (1,2,3, and 4), each containing 2 beds (A and B). Three pairs of twins are being studied tonight. Each pair of twins will be assigned to one of the four rooms, and then each twin will be assigned a specific bed in the room. How many ways are there to organize the experiment? (i.e. How many ways are there to assign the 6 subjects to rooms and beds if each pair of twins must share the same room?) 24 8 192 48 12

To investigate whether it helps to have a "white-sounding" first name when looking for a job, the researchers sent 5,000 resumes in response to ads that appeared in magazines. The resumes were identical except that 2,500 of them had "white-sounding" first names, such as Brett and Emily, whereas the other 2,500 had "black-sounding" names such as Tamika and Rasheed. Resumes of the first type elicited 251 responses and resumes of the second type only 169 responses. A button hyperlink to the SALT program that reads: Use SALT. Do these data support the theory that the proportion receiving responses is greater for those resumes with "white-sounding first" names? (Use ? = 0.05. Use pwhite-sounding − pblack-sounding.) Find the test statistic. (Round your answer to two decimal places.) z = Find the P-value. (Round your answer to four decimal places.) P-value = State your conclusion. Reject H0. We have convincing evidence that the proportion eliciting responses is higher for…

Should you have a cup of coffee to make you more alert when studying for a big test? A researcher is interested in studying the effect of caffeine, and he comes up with the following plan for an experiment. The experiment will involve 100 volunteers each of which will take a memory test 20 minutes after drinking cola. Some volunteers will be randomly assigned to drink caffeine-free cola; some to drink regular cola (with caffeine), and the others a mixture of the two (getting a half dose of caffeine). For each volunteer, a test score (the number of items recalled correctly) will be recorded. The volunteers will not be told which type of cola they have been given, but the researcher who evaluates the results will prepare the cups of cola right on the spot (out of sight of the volunteers).(a) What type of design is this experiment?             (b) The treatments are             (c) The score of the memory test is the ?             (d) The study finds that the group of students who drink…

250 adults are practicing every day before taking part in a high-stakes children's game. The game requires them carefully to remove a shape- either a star or an umbrella-from a sugar wafer. 30% of those who choose stars on a given day will switch to umbrellas the next day, and 20% of those who choose umbrellas on a given day will switch to stars the next day. (a) If 150 contestants practice with stars today, how many will practice with umbrellas tomorrow? (b) If the actual game is held a long time from now, what proportion of contestants do we expect will be practicing with stars each day close to then?

Diana tested the effect of number of items on short-term memory in dolphins.  She randomly presented visual arrays with 1, 2, 3, 5, 8, 13, 21 items for five minutes.  She asked 3 dolphins to remember the items. She then presented a new array with old and new items.  The dolphins responded by touching the items with their tails.  She hypothesized that Dolphins could remember 3 items accurately, but not more than that.  How many pairwise comparisons should she do according to the recommended guideline?

A recent study sought to determine if exercising after studying for an exam may help retain information. The 150 student volunteers that participated in the study were randomly assigned to three groups. All students were given a picture memory task that they studied for 15 minutes. After studying, one of the groups was instructed to exercise for 30 minutes immediately after studying. A second group was instructed to wait 1 hour after studying and then exercise for 30 minutes. The third group was instructed to not exercise after studying. The next day all 150 student volunteers were given a test to determine how well they could remember what they studied. Here are the results:   The researchers want to test: H0: There is no difference in the distribution of performance on the test for the three treatment groups among the population of all student volunteers like these. Ha: There is a difference in the distribution of performance on the test for the three treatment groups among the…