Solution to question 11.1
The first study indicated that there was not a significant difference between the toothpastes (the 95% CI included 0 and also P = 0·131). The second study indicated that there was a significant difference. The reason for this is probably the difference in sample sizes. The fist study only looked at ten subjects per group and thus probably had low power, i.e. there was a high chance of a type 2 error (false negative). The second study had a much higher sample size and consequently will have had a higher power, making the chance of a false negative much lower.
We can be quite confident that there is a difference between the two toothpastes
