Question

Assume that different groups of couples use a particular method of gender selection and each couple gives birth to one baby. This method is designed to increase the likelihood that each baby will be a​ girl, but assume that the method has no​ effect, so the probability of a girl is 0.5. Assume that the groups consist of 26 couples. Complete parts​ (a) through​ (c) below. a. Find the mean and the standard deviation for the numbers of girls in groups of 26 births. The value of the mean is muequals nothing. ​(Type an integer or a decimal. Do not​ round.) The value of the standard deviation is sigmaequals nothing. ​(Round to one decimal place as​ needed.) b. Use the range rule of thumb to find the values separating results that are significantly low or significantly high. Values of nothing girls or fewer are significantly low. ​(Round to one decimal place as​ needed.) Values of nothing girls or greater are significantly high. ​(Round to one decimal place as​ needed.) c. Is the result of 23 girls a result that is significantly​ high? What does it suggest about the effectiveness of the​ method? The result ▼ is not is significantly​ high, because 23 girls is ▼ less than equal to greater than nothing girls. A result of 23 girls would suggest that the method ▼ is effective. is not effective. ​(Round to one decimal place as​ needed.)

Answer 1

a) Mean = n * p = 26 * 0.5 = 13

Standard deviation = sqrt(np(1 - p))

                               = sqrt(26 * 0.5 * 0.5)

                               = 2.6

b) Significantly low =

                              = 13 - 2 * 2.6 = 7.8

Significantly high =
                              = 13 + 2 * 2.6 = 18.2

c) Yes the result of 23 girls is significantly high, because 23 girlls is greater than 18.2 girls.

A result of 23 girls would suggest that the method is not effective.