All 250 of the citys Democratic ward leaders were polled about the nu

All 250 of the city’s Democratic ward leaders were polled about the number of registered Republicans who became registered Democrats during the year. From the reports of the 20 leaders who replied to the questionnaire, we know that altogether they received a total of 500 former Republicans into the Democratic party within the year. Projecting from this sample, we conclude that at least 6,000 Republicans became Democrats during the year.

Which one of the following statements, if true, most clearly undermines the conclusion?

(A) Several years ago, 5,000 members of the Republican party registered as Democrats. - What happened several years ago has no bearing on the current situation

(B) The more than 90 percent of ward leaders not replying had no former Republicans registering as Democrats. - Correct - Since if other 90% leaders who didn't reply had no republicans then the conclusion will fail which is based on extrapolation of the rather very small sample.

(C) Because they were too busy, more than 90 percent of the ward leaders did not reply. - Doesn't matter at all

(D) A number of the newly registered Democrats returned to the Republican party at a later date. - Case could be that there were 10000 republicans and 4000 returned in which case the conclusion would still be valid - Incorrect

(E) Similar figures can be produced from past years for registration changes from the Democratic party to the Republican party. - What happened in past years has no bearing on the current situation

Answer - B

All 250 of the city’s Democratic ward leaders were polled about the number of registered Republicans who became registered Democrats during the year. From the reports of the 20 leaders who replied to the questionnaire, we know that altogether they received a total of 500 former Republicans into the Democratic party within the year. Projecting from this sample, we conclude that at least 6,000 Republicans became Democrats during the year.

Which one of the following statements, if true, most clearly undermines the conclusion?

(A) Several years ago, 5,000 members of the Republican party registered as Democrats. - WRONG. Old one off data not helpful.

(B) The more than 90 percent of ward leaders not replying had no former Republicans registering as Democrats. - CORRECT. Already if there are no Republicans then it is established that that claim is wrong in conclusion.

(C) Because they were too busy, more than 90 percent of the ward leaders did not reply. - WORNG. May or may not be strengthening depending upon whether there were republicans or not.

(D) A number of the newly registered Democrats returned to the Republican party at a later date. - WRONG. Irrelevant.

(E) Similar figures can be produced from past years for registration changes from the Democratic party to the Republican party. - WRONG. Strengthens somewhat if at all to be considered.

Answer B.