Question

A catalog sales company promises to deliver orders placed on the Internet within 3 days.​ Follow-up calls to a few randomly selected customers show that a 90​% confidence interval for the proportion of all orders that arrive on time is 88​% ±4​%. What does this​ mean? Are the conclusions below​ correct? Explain.

a) Between 84​% and 92​% of all orders arrive on time.
b)	90​% of all random samples of customers will show that 88​% of orders arrive on time.
c)	90​% of all random samples of customers will show that 84​% to 92​% of orders arrive on time.
d)	The company is 90​% sure that between 84​% and 92​% of the orders placed by the customers in this sample arrived on time.
e)	On 90​% of the​ days, between 84​% and 92​% of the orders will arrive on time.

Answer 1

(a)

Not correct

Explanation:

90% Confidence Interval is 88%4% means: On 90​% of the​ days, between 84​% and 92​% of the orders will arrive on time.

(b)

Not correct

Explanation:

90% Confidence Interval is 88%4% means: On 90​% of the​ days, between 84​% and 92​% of the orders will arrive on time.

(c)

Not correct

Explanation:

90% Confidence Interval is 88%4% means: On 90​% of the​ days, between 84​% and 92​% of the orders will arrive on time.

(d)

Not correct

Explanation:

90% Confidence Interval is 88%4% means: On 90​% of the​ days, between 84​% and 92​% of the orders will arrive on time.

(e)

Correct

Explanation:

90% Confidence Interval is 88%4% means: On 90​% of the​ days, between 84​% and 92​% of the orders will arrive on time.