PSY-520 Topic 2 Exercises – Chapters 5 & 8 with Answers

PSY-520 Topic 2 Exercises – Chapters 5 & 8 with Answers 5.11 Scores on the Wechsler Adult Intelligence Scale (WAIS) approximate a normal curve with a mean of 100 and a standard deviation on 15. What proportion of the IQ scores are a. above Kristen’s 125? z= 125-100/15= 1.67 using the z table on page 536 = 0.0475 b. below 82? z=82-100/15 = -1.2 C’=0.1151 c. Within 9 points of the mean? 100 +9=/15=0.6 100-9=91 91-100/15=-0.6 B+B’ .2257+.2257 =0.4514 d. More than 40 points from the mean? 100+40=/15=2.67 100-40=60 60-100/15=-2.67 C+C’ .0038+.0038 =0.0076 5.13 IQ scores on the WAIS test approximate a normal curve with a mean of 100 and a standard deviation of 15. What IQ score is identified with a. the upper 2 percent, that is, 2 percent to the right (and 98 percent to the left)? Look in Column C for closest value to 0.02 Z=2.05 has C=0.0202 100+2.05*15 =130.75=greater than 131 lower 10 percent? Look in Column C’ for closest value to 0.1 Z=1.28 has C’=.1003 100-1.28*15 =80.8= less than 81 c. the upper 60 percent? Look in Column C’ for closest value to 0.4 Z=0.25 has C’=0.4013 100-0.25*15 =103.75= greater than 104 d. the middle 95 percent? B+B’=0.475 Z=1.96 for B=B’=.475 100-1.96*15 70.6 100+1.96*15 129.4 Between 71-130 E the middle 99 percent? B+B’=0.495 Z=2.57 for B=B’=..57*15 61.45 100+2.57*15 138.55 Between 61-139 5.15 An investigator polls common cold sufferers, asking them to estimate the number of hours of physical discomfort caused by their most recent colds. Assume that their estimates approximate a normal curve with a mean of 83 hours and a standard deviation of 20 hours. a. What is the estimated number of hours for the shortest suffering 5 percent? Use z table to find C’ value as close to 0.05 as possible. Using Z=1.64 X=83-(1.64*20) X=less than 50.2 hours b. What porortion of sufferers estimate that their colds lasted longer than 48 hours? Z=48-83/20 Z=-1.75 from table C’=0.0505 1-C’=0.9599 c. What proportion suffered for fewer than 61 hours? Z=61-83/20=-1.1 C’=0.1357 from z table d. What is estimated number of hours suffered by the extreme 1 percent either above or below the mean? Z=2.33 for C=0.009 from z table 83+2.33*20=129.6 83-2.33*20=36.4 e. What proportion suffered for between 1 and 3 days, that is, between 24 and 72 hours? =0.2912-0.0016 from z tables =0.2896 f. What is the estimated number of hours suffered by the middle 95 percent? Look for B=B’=0.475 Z=1.96 83+1.96*20=122.2 83-1.96*20=43.8 g. What proportion suffered for between 2 and 4 days? 96-83/20=0.65 48-83/20=-1.75 From z tables for B and B’ B=0.4599 & B’=0.2422 =0.7021 h. A medical researcher wishes to concentrate on the 20 percent who suffered the most. She will only work with those who estimate that they suffered for more than _ hours? 0.84 =z from z table C = 0.2005 83+0.84*20=99.8 i. Another researcher wishes to compare those who suffered the least with those who suffered the most. If each group is to consist of only the extreme 3 percent, the mild group will consist of those who suffered for fewer the _ hours, and the severe group will consist of those who suffered more than _ hours? Z= 1.88 for C=C’=0.0301 83+1.88*20= 120.6 83-1.88*20= 45.4 j. Another survey found that people with colds who took daily doses of vitamin C suffered for 61 ho