Question

At what age do infants speak their first word of English? Here are the data on 20 normal children (ages in months). Assume that the distribution of the age at which all children speak their first word (the population) is normal. 15 14 10 9 15 20 18 11 8 11 11 9 10 11 11 10 12 17 11 10 a) First, create a histogram of the data above using StatCrunch and include and attach it to your exam. Describe the shape. [2 points] b) Is there good evidence that the mean age at first word among all normal children is greater than 12 months? Conduct a hypothesis test at the α = 0.05 level of significance to determine this. [8 points] For full credit, make sure to show all 4 steps:

i) Hypothesize

ii) Prepare (level of significance and test that the conditions are met)

iii) Compute the test statistic and the p-value and include a sketch showing the p-value

iv) Write a sentence that interprets your results in context

Answer 1

(iv) There is insufficient evidence to support the claim that the mean age at first word among all normal children is greater than 12 months.