438 CHAPTER 8 Hypothesis Testing Cooperative Group Activities 1.In-class activity The “psychic staring effect”: Can you sense when someone is staring at you? Pair off students and conduct an experiment to test this effect. For each pair of students, one student is the subject being stared at, and the other is the student who does (or does not) stare and cannot be seen by the subject. Each pair of students should conduct ten trials in which some of the trials involve staring and the others do not. In each trial, the subject must identify whether staring is occurring. Select the trials using random selection, such as tossing a coin to determine when staring is used. Combine all of the results and use them to test the claim that the proportion of correct responses by the subjects is p = 0.5, which corresponds to random guesses. What do you conclude about the psychic staring effect? 2.Out-of-class activity The author was told that 1962 pennies are biased in this sense: When they are made to stand on the edge and the table is bumped, heads will occur 80% of the time. Obtaining a sample of 1962 pennies may be challenging, so groups of three or four students may use a sample of any pennies to test that claim. What do you conclude? 3.Out-of-class activity Exercise 10 in Section 8-2 deals with results from the MythBusters television show in which buttered toast was dropped. The goal was to determine whether dropped buttered toast lands with the buttered side down at a rate significantly different from 50%. In groups of three or four, replicate the MythBusters experiment by creating your own experiment to test the claim that buttered toast lands with the buttered side down at a rate significantly different from 50%. 4.Out-of-class activity How do you draw the letter X? Working in groups of three or four, randomly select subjects and ask them to draw the letter X. Observe how the X is drawn, and record whether it is drawn by starting at the top left side and drawing ∖, then starting at the top right side and drawing >. Test the claim that the majority of people draw the X as described here. 5.Out-of-class activity Here is the breakdown of the most common car colors from PPG Industries: 23% are white, 18% are black, 16% are gray, 15% are silver, and 10% are red. After selecting one of the given colors, groups of three or four students should go to the college parking lot and randomly select cars to test the claim that the percentage for the chosen color is as claimed. 6.Out-of-class activity In the United States, 40% of us have brown eyes, according to Dr. P. Sorita Soni at Indiana University. Groups of three or four students should randomly select people and identify the color of their eyes. The claim that 40% of us have brown eyes can then be tested. 7.In-class activity Without using any measuring device, each student should draw a line believed to be 3 in. long and another line believed to be 3 cm long. Then use rulers to measure and record the lengths of the lines drawn. Find the means and standard deviations of the two sets of lengths. Test the claim that the lines estimated to be 3 in. have a mean length that is equal to 3 in. Test the claim that the lines estimated to be 3 cm have a mean length that is equal to 3 cm. Compare the results. Do the estimates of the 3-in. line appear to be more accurate than those for the 3-cm line? What do these results suggest? 8.In-class activity Assume that a method of gender selection can affect the probability of a baby being a girl so that the probability becomes 1>4. Each student should simulate 20 births by drawing 20 cards from a shuffled deck. Replace each card after it has been drawn, then reshuffle. Consider the hearts to be girls and consider all other cards to be boys. After making 20 selections and recording the “genders” of the babies, use a 0.10 significance level to test the claim that the proportion of girls is equal to 1>4. How many students are expected to get results leading to the wrong conclusion that the proportion is not 1>4? How does that relate to the probability of a type I error? Does this procedure appear to be effective in identifying the effectiveness of the gender selection method? (If decks of cards are not available, use some other way to simulate the births, such as using the random number generator on a calculator or using digits from phone numbers or Social Security numbers.)
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