A study was conducted to investigate the age at first birth for women who have thrombocytopenia (low platelet count). Investigators hypothesize that these women with thrombocytopenia may be at increased risk of miscarriage, which could impact their age at first birth, so these mothers are older at their first birth.

Suppose we know that the average age for first birth in the general population of women is 26.5 years. Investigators are interested in whether the average age among women with thrombocytopenia in the population is 26.5 years or if their average is something higher than 26.5 years.

Thus H0: The average age at first birth for women with thrombocytopenia is 26.5 years in the population Ha: The average age at first birth for women with thrombocytopenia is greater than 26.5 years in the population They found xbar = 27.1 years, t=0.79, p=0.22.

(Alpha =0.05)

Which of the following could be the associated 95% CI? (You should not need to COMPUTE the CI! You should be able to tell by looking, or perhaps sketching, the choices.)

a. (28.2,29.4)

b. (25.6, 26.6)

c. (26.6 ,27.6)

d. (25.6, 28.6)