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

step by step resolutions

1) n+n+1+n+2=51

3n+3=51

3n=48

n=16

the three numbers are 16, 17 and 18.

2) x+15=4x

3x=15

x=5

radha is now 5 years old

3) the two digits are x and y.

y=3x

(10x+y)+(10y+x)=88

y=3x

11x+11y=88

y=3x

x+y=8

x+3x=8

x=2

the original number can be either 28 or 82.

4) n+(n+2)+(n+4)=48

3n+6=48

3n=42

n=14

the numbers are 14, 16 and 18.

5) y=x+3

10y+x+10x+y=143

y=x+3

11x+11y=143

y=x+3

x+y=13

x+x+3=13

2x=10

x=5

the original number can be 57 or 75.

hope this !