As part of its twenty-fifth reunion celebration, the Class of 1980 of State Univ
ID: 3202689 • Letter: A
Question
As part of its twenty-fifth reunion celebration, the Class of 1980 of State University mailed a questionnaire to its members. One of the questions asked the respondent to give his or her total income last year. Of the 820 members of the class of 1980, the university alumni office had addresses for 583. Of these, 421 returned the questionnaire. The reunion committee computed the mean income given in the responses and announced, "The members of the class of 1980 have enjoyed resounding success. The average income of class members is $120,000!". Identify two distinct sources of bias or misleading information in this result, being explicit about the direction of bias you expect. Explain how you might fix each of these problems.Explanation / Answer
The two sources of bias are:
Firstly: the data contains only 583 contacts that can be approached. This rings in the first bias.
This may cause a bias in any direction. The salary might increase or decrease by adding the missing contacts to the data.
The only way to reach or cover this lapse is, by contacting the missing data with the help of other classmates or trying to reach their native contact , when they were studying. This may for sure , add up more people into the response data, and thereafter result in the accurate average earning of the batch.
.
The second bias, originates from the no response of (583-421 = 162 people) .
This may be possibly , because they earn less, and would hesitate reporting their earnings. This may lead to an illusionary hike in the average salary.
the best way to remove this bias, is by calling them personally and assuring that this data is only for calculating the average success rate of the batch , and would not be disclosed to any one else. Such a step may induce better response , and would thereby help reducing the bias.
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