QUESTION 11 An ethologist is interested in how long it takes a certain species of water shrew to catch its prey. On 50 occasions each day he lets a dragonfly loose inside the cage of the shrew and times how long it takes until the shrew catches the dragonfly. After months of research the ethologist concludes 1) that the mean prey catching time was 45 seconds, 2) the standard deviation was 7 seconds and 3) that the scores he has collected are normally distributed. (Note: remember that the proportions in the Z-table can also be viewed as probabilities.) Based on the shrew’s past record, what is the probability:

a) it will catch a dragonfly in less than 21 seconds;