Suppose that replacement times for washing machines are normally ...

[chads108]

Suppose that replacement times for washing machines are normally distributed with a mean of 9.2 years and a standard deviation of 1.2 years. Find the 82nd percentile.
 
  A) 9.7 years B) 10.3 years C) 8.1 years D) 9.4 years

Question 2

7 of 8500 people vaccinated against a certain disease later developed the disease. 18 of 10,000 people vaccinated with a placebo later developed the disease.
 
  At the 2 significance level, do the data provide sufficient evidence to conclude that those who are vaccinated against the disease are at lower risk of developing the disease than those vaccinated with a placebo?

[ApricotDream]

Answer to Question 1

B

Answer to Question 2

H0: p1 = p2, Ha: p1 < p2.
 = 0.02
Test statistic: z = -1.80. Critical value = -2.05.
Do not reject the null hypothesis. At the 2 significance level the data do not provide sufficient evidence to conclude that those who are vaccinated against the disease are at lower risk of developing the disease than those vaccinated with a placebo.

[chads108]

Gracias!

[strudel15]

Excellent