A 95 confidence interval for the difference of the mean numb

A 95% confidence interval for the difference of the mean number of times race horses are lame and the number of times horses used for jumping are lame over a 12-month period [u(race) - u (jump) is calculated to be (-2.13, 3.47). Therefore, it can be concluded that:

a. a confidence interval cannot contain negative and positive values, no conclusion can be drawn

b. it is highly likely that race horses are lame more often than jumping horses since the interval contains more positive than negative values

c. the sample is too small to come to any conclusion

d. race horses and jumping horses are on average equally often lame because the confidence interval contains zero.

Solution

(D) is correct because it is plausible that mean difference is zero since the CI contains zero.