Eric wants to estimate the percentage of elementary school children who have a social media account. he surveys 450 elementary school children and finds that 280 have a social media account. identify the values needed to calculate a confidence interval at the 99% confidence level. then find the confidence interval.

The confidence interval for population mean is given by :-

, where is the sample proportion, n is the sample size , is the critical z-value.

The  values needed to calculate a confidence interval at the 99% confidence level are :

Given : Significance level :

Sample size : n=450

Critical value :

Sample proportion:

Now, the  99% confidence level will be :

Hence, the  99% confidence interval is

answer: 4

step-by-step explanation:

b. 1.25 hr

step-by-step explanation:

if you have a constant speed of 60 mph, then you have a ratio between 60 mi. to 1 hr. dividing both sides by 60 we get the ratio

1 mi. to

then mult. both sides by 75 we get the ratio

75 mi. to

simplifying we get

75 mi. to

or 1.25 hr.