Question

The accompanying table describes results from groups of 10 births from 10 different sets of parents. The random variable x represents the number of girls among 10 children. Use the range rule of thumb to determine whether 1 girl in 10 births is a significantly low number of girls.

x   P(x)
0   0.001
1   0.017
2   0.036
3   0.113
4   0.207
5   0.241
6   0.207
7   0.113
8   0.037
9   0.012
10   0.016

Answer 1

Ans:

x	P(x)	x*P(x)	(x-5.058)^2*P(x)
0	0.001	0	0.0256
1	0.017	0.017	0.2799
2	0.036	0.072	0.3366
3	0.113	0.339	0.4786
4	0.207	0.828	0.2317
5	0.241	1.205	0.0008
6	0.207	1.242	0.1837
7	0.113	0.791	0.4262
8	0.037	0.296	0.3202
9	0.012	0.108	0.1865
10	0.016	0.16	0.3908
Total	1	5.058	2.8606

mean=5.058

standard deviation=sqrt(2.8606)=1.7

lower limit=5.1-2*1.7=1.7

upper limit=5.1+2*1.7=8.5

As,one girl is lower than the lower limit of range of usual number of girls,so 1 girl in 10 births is a significantly low number of girls.