Question

1.Find the critical value t_α/2 needed to construct a confidence interval of the given level with  given sample size.
Level 90%, sample size 21

Group of answer choices

1.725

1.325

1.721

1.645

2.  

Find the probability P(-0.62 < z < -0.01) using the standard normal distribution.

Group of answer choices

0.2284

0.3584

0.7716

0.1900

Answer 1

Solution :

Given that,

1.

sample size = n = 21

Degrees of freedom = df = n - 1 = 21 - 1 = 20

At 90% confidence level the t is ,

= 1 - 90% = 1 - 0.90 = 0.1

/ 2 = 0.1/ 2 = 0.05

t /2,df = t0.05,20 = 1.725

he critical value tα/2 = 1.725

2.

Using standard normal table ,

P(-0.62 < z < -0.01)

= P(z < -0.01) - P(z < -0.62)

= 0.496 - 0.2676

= 0.2284

P(-0.62 < z < -0.01) = 0.2284