Question 1

If the sample standard deviation is known and the sample size is small (n<20), the confidence interval for the normally distributed population mean (), based on the

A.t-distribution

B.normal distribution

C.binominal distribution

D.Poisson distribution

Question 2

Suppose that we want to find the t-values (critical values) of a random sample of 30 observations at the significance level of 0.01 for a two tailed test. In Excel, which of the following function can be used to generate the correct values?

A.T.INV(0.01,30)

B.T.INV(0.005,30)

C.T.INV.2T(0.005,29)

D.T.INV.2T(0.01,29)

Question 3

Suppose that we want to test:

H₀: = ₀

H₁: < ₀

If t-score (test statistic) is 1.75, with the significance level (alpha) = 0.05 and sample size (n) =30, we then:

A.Reject H₀ at the 5% significance level

B.Do not reject H₀ at the 5% significance level

C.Reject H₁ at the 5% significance level

D.Do not reject H₁ at the 5% significance level

Question 4

In a sample of 51 iPhones, 18 had over 94 apps downloaded. Construct a 99% confidence interval for the population proportion of all iPhones that obtain over 94 apps.

A.0.18 0.17

B.0.18 0.09

C.0.35 0.16

D.0.35 0.17

Question 5

In a sample of decorative 32 bulbs, 8 were defective. The lower confidence limit at the 98% confidence level for the population proportion of defective bulbs is

A.0.250

B.0.072

C.0.428

D.0.175