For each of the following studies, identify the source(s) of sampling bias and describe (i) how it might affect the study conclusions and (ii) how you might alter the sampling method to avoid the bias. (a) To study the size distribution of rock cod (Epinephelus puscus) off the coast of southeastern Australia, scientists recorded the lengths and weights for all cod captured by a commercial fishing vessel on one day (using standard hook-and-line fishing methods).
(b) A nutritionist is interested in the eating habits of college students and observes what each student who enters a dining hall between 8:00 A. M. and 8:30 A. M. chooses for breakfast on a Monday morning.
(c) To study how fast an experimental painkiller relieves headache pain residents of a nursing home who complain of headaches are given the painkiller and are later asked how quickly their headaches subsided.

A first of all because the sample involves only rock cods that voluntarily get hooked to the fishing rod, this is a major source of bias as the sample does not represent the whole general population.

Rather adopt stratified sampling stratified basing on Geographical location can be suggested for this study.

II. Because convenient sampling is adopted here data is only gotten from students that eat in the hall in a given period of time so this is a source of bias

Also one study center that is the Hall of only one school is used this is also biased and may affect the result of the study

To avoid this bias a simple random sampling where each student have an equal chance of being selected in the study should be adopted

Iii. this study is using convenient samples. and the effect of head ache medicine may be affected by other medicines too so the headache medicine cannot be the only reason for painrelief so it is better to sample rando amongst patients with headache

the correct answer would be c