Find the z test statistic in the following problems and show calculations. 1.In

Question

Find the z test statistic in the following problems and show calculations.

1.In a study of treatments for very painful "cluster" headaches, 141 patients were treated with oxygen and 160 other patients were given a placebo consisting of ordinary air. Among the 141 patients in the oxygen treatment group, 122were free from headaches 15 minutes after treatment. Among the 160 patients given the placebo, 35 were free from headaches 15 minutes after treatment. Use a 0.05 significance level to test the claim that the oxygen treatment is effective.

2.In a random sample of males, it was found that 21 write with their left hands and 218 do not. In a random sample of females, it was found that 65 write with their left hands and 450 do not. Use a 0.01 significance level to test the claim that the rate of left-handedness among males is less than that among females.

Explanation / Answer

1)

p1= 122 / 141= 0.865

p2 = 35 /160 = 0.22

P = ( 122+35) / (141+160) = 0.52

Z = ( 0.865 - 0.22) / SRQT (0.52*0.48 * ( 1/141 + 1/160 )

Z = 11.17

2)

p1 = 21 / (21+218) = 0.088

p2 = 65 / (65+450) = 0.126

P = ( 21+65) / (21+218+65+450) = 0.114

Z = 0.126 - 0.088 / ( srqt ( 0.114*0.886* 1 / 239 + 1/515 )

Z = 1.53

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