6.135 Welfare reform.
A study compares two groups of mothers with young children who were on welfare two years ago. One group attended a voluntary training program offered free of charge at a local vocational school and advertised in the local news media. The other group did not choose to attend the training program. The study finds a signifcant difference () between the proportions of the mothers in the two groups who are still on welfare. The difference is not only signifcant but quite large. The report says that with 95% confidence the percent of the nonattending group still on welfare is higher than that of the group who attended the program. You are on the staff of a member of Congress who is interested in the plight of welfare mothers and who asks you about the report.
6.135
(a) The difference between the groups is so large that we do not believe it is attributed to chance. (b) 95% confidence means our results, in the long run, will be correct 95% of the time. (c) Not necessarily because there likely are lurking variables. For example, it is possible that those mothers willing to sign up for the training program are also more actively seeking employment, which could account for the difference.