Question

What was the age distribution of prehistoric Native Americans? Extensive anthropological studies in the southwestern United States gave the following information about a prehistoric extended family group of 93 members on what is now a Native American reservation. For this community, estimate the mean age expressed in years, the sample variance, and the sample standard deviation. For the class 31 and over, use 35.5 as the class midpoint. (Round your answers to one decimal place.) Age range (years) 1-10 11-20 21-30 31 and over Number of individuals 36 23 23 11 x = s2 = s =

Answer 1

midpoint(X)	Frequency(f)	Freq*X	(X-mean)	(X-mean)2	f*(X-mean)2
5.5	36	198	-10.968	120.291	4330.489
15.5	23	356.5	-0.968	0.937	21.54
25.5	23	586.5	9.032	81.582	1876.379
35.5	11	390.5	19.032	362.227	3984.495
Total ->	93	1531.5	-	-	10212.903

Mean =   fx / f

= 1531.5 / 93

= 16.468

= 16.5

Variance = ( f*(X-mean)2 / n- 1 )

= ( 10212.903 / 92 )

= 111.01

= 111

Standard Deviation = sqrt ( 111.01 )

= 10.536

= 10.5