Answer:
Sample size of at least 49 must be needed .
Step-by-step explanation:
We are given that a 98% confidence interval is constructed with a margin of error equal to 3,000 miles. Assume the standard deviation for the tire life of this particular brand is 9,000 miles.
So, Margin of error formula is given by =
where, = significance level which is 2%
= standard deviation = 9,000 miles
n = sample size
Here, the value of z score at 2% significance level is 2.3263 .
So, margin of error = 2.3263 *
=
= 6.9789
n = = 48.7 or ≈ 49 (approx)
Therefore, sample size of at least 49 must be needed .