Question

Question 28 3 pts Suppose that the graduation rate in a school district is 85 percent. A random sample of students from the district are selected to participate in a mentoring program. Among this group of 100 students, 90 students graduate. The statistic for this hypothesis is ; therefore, you reject the null at the 5-percent level of significance and you conclude that the program is in increasing graduation rates. ot; 1.57; can; effective o Z; 2.80, can; effective t; 3.24; cannot: not effective o Z; 1.40; cannot; not effective Question 29 3 pts On a national achievement test with a population that is normally distributed with a population mean of 175 points and a population standard deviation of 50 points, Jo has a Z-score on this test of -0.5. What is her numerical score on this test? O 125 o 175 O 200 150 Question 30 3 pts Assume that the underlying population is normally distributed. Suppose that you have a random sample of 25 individuals with a sample mean of 30 and a sample variance of 100. The 95-percent confidence interval for the population mean is approximately: 24.45 to 35.55 o 27.94 to 32.06 o 28.04 to 31.96 o 25.87 to 34.13

Answer 1

28)

Null Hypothesis : Mean = 85%

Alternate Hypothesis : Mean != 85%

Standard deviation of 85, 1s and 15, 0s is 0.3589

Standard error of sample size 100 = standard deviation/ sqrt(100) = 0.03589

Sample mean = 90%

Sample statistic (z) = (90% - 85%)/standard error = 1.4

So, Option D looks good.

29)

Mean = 175

Standard deviation = 50

z score = -0.5

Actual score = Mean + z score*standard deviation = 175 - 0.5*50 = 150

Option D looks good.

30)

sample size = 25

sample mean = 30

sample variance = 100

degree of freedom (df) = n - 1 = 25 - 1 =24

95% confidence interval

t stat for 95% confidence interval and df as 24 = 2.0639

sample standard deviation = sqrt(sample variance) = sqrt(100) = 10

sample standard error = sample standard deviation/sqrt(n) = 10/sqrt(25) = 2

confidence interval

(mean - t*standard error, mean + t*standard error)

(30 - 2.0639*2, 30 + 2.0639*2)

(25.87 , 34.13)

Option D looks good.

Please like, if you understood. Thanks.