Question

Researchers were interested in the effects of mothers breastfeeding. They thought that it would have an effect on intelligence in children. They sampled 25 10-year-old children whose mothers had breastfed exclusively for the first 6 months of their children's lives and gave them the full-scale Wechsler Intelligence Scale for Children - V Canadian edition (WISC-VCdn). In a typically developing population in Canada, the WISC-VCdn has a mean of 100 and a standard deviation of 15. The researchers believed that breastfeeding might increased intelligence test scores for the children. When they averaged the WISC-VCdn scores for the 25 children who were tested, they found a mean IQ of 106.5. What type of test should they use to test this hypothesis? An independent samples t-test, a z-test, a dependant sample t-test, or a single sample t-test?

Answer 1

Sol:

Ho:mu=100

Ha:mu>100

alpha=0.05

Its a z test since population standard deviation is given

Z=xbar-mu/sigma/sqrt(n)

=(106.5-100)/15/sqrt(25)

z= 2.166667

z crit for 95%=1.96

z stat>z crit

Reject Ho

ANSWER:

z test