Question

Gibbs Baby Food Company wishes to compare the weight gain of infants using its brand versus its competitor's. A sample of 40 babies using the Gibbs products revealed a mean weight gain of 7.6 pounds in the first three months after birth. For the Gibbs brand, the population standard deviation of the sample is 2.3 pounds. A sample of 55 babies using the competitor's brand revealed a mean increase in weight of 8.1 pounds. The population standard deviation is 2.9 pounds.

1. State the decision rule for 0.05 significance level : H₀: μ_Gibbs ≥ μ_Competitor; H₁: μ_Gibbs < μ_Competitor. (Negative value should be indicated by a minus sign. Round your answer to 2 decimal places.)

2. Compute the value of the test statistic. (Negative value should be indicated by a minus sign. Round your answer to 2 decimal places.)

3. Compute the p-value. (Round your answer to 4 decimal places.)

4. Can we conclude that babies using the Gibbs brand gained less weight? Use the 0.05 significance level.

Answer 1

a)

Decision rule :                   reject Ho if test statistic z<-1.64

b)

value of the test statistic z =-0.94

c)

p-value =0.1736

d)

as p value is greater than 0.05 level

we can not conclude that babies using the Gibbs brand gained less weight