Question

A frequency distribution for the response time for EMTs after a 911 call is shown below.

Response Time for EMTs

Response Time (in minutes)	Frequency fifi
8 – 8.9	23
9 – 9.9	21
10 – 10.9	30
11 – 11.9	49
12 – 12.9	47
13 – 13.9	32
14 – 14.9	23

Step 2 of 2 :  

Calculate the population variance for the response time. Round any intermediate calculations, if needed, to no less than four decimal places, and round your final answer to two decimal places.

Answer 1

Solution =

Group	Midpoint X	Frequency f	f*x	x^2	f*(x^2)
8 to 8.9	8.45	23	194.35	71.4025	1642.258
9 to 9.9	9.45	21	198.45	89.3025	1875.353
10 to 10.9	10.45	30	313.5	109.2025	3276.075
11 to 11.9	11.45	49	561.05	131.1025	6424.023
12 to 12.9	12.45	47	585.15	155.0025	7285.118
13 to 13.9	13.45	32	430.4	180.9025	5788.88
14 to 14.9	14.45	23	332.35	208.8025	4802.458
SUM		225	2615.25	945.7175	31094.16

= = 2615.25/225 = 11.6233

Variance =  

= [31094.16/225] - [11.62332 ]

= 3.09516377667

Variance = 3.09516377667 = 3.10

Answer :

Population variance = 3.10