1. Why does the variance calculated from a sample have to be corrected to give a realistic indication of the variance of the population from which it has been taken?
2. An sample of 16 adult weaver rats, Rattus weaveri, found in a storage freezer in a museum and only labelled 'Expedition to North and South Keppel Islands, 1984: all from site 3' had a mean body weight of 875 grams. The mean body weight for the population of adult weaver rats on North Keppel Island is 1000 grams (1 kg), with a standard deviation of 400 grams and the population on South Keppel Island has a mean weight of 650 grams and a standard deviation of 400 grams. (a) From these population statistics, calculate the SEM and the range within which you would expect 95% of the means for samples of 16 rats from each population. (b) Which of the two islands is the sample most likely to have come from? (c) Please discuss.