Question

What is the t-value for a 90% confidence interval for the mean if the sample size is 24?

a. 1.984 b. 1.714 c. 2.069 d. 1.96 e. 2.306

In general, when choosing the sample size for estimating a mean, which of the following will result in a smaller margin of error (E)?

	a.	a larger confidence level
	b.	a smaller sample size
	c.	a dozen glazed donuts
	d.	a larger sample size
	e.	a more expensive calculator

Answer 1

Given That :

Confidence Interval = 90%

N= 24

Degree of Freedom Df = n-1 = 1-24 = 23

,df

t_{0.1/2 , df} = t_{0.05, 23}

From t table

one tail test

t value at df = 23 p=0.05

t value = 1.714

Hence option b is correct

2)

Margin of Error (E) =

To get smaller Margin error we should increase sample size

So answer is a larger sample size

Hence option d is correct