TABLE 14-2
A political pollster randomly selects a sample of 100 voters each day for 8 successive days and asks how many will vote for the incumbent. The pollster wishes to construct a p chart to see if the percentage favoring the incumbent candidate is too erratic.
-Referring to Table 14-2, what is the numerical value of the center line for the p chart?
A) 0.53
B) 0.56
C) 0.63
D) 0.66

Question

TABLE 14-2
A political pollster randomly selects a sample of 100 voters each day for 8 successive days and asks how many will vote for the incumbent. The pollster wishes to construct a p chart to see if the percentage favoring the incumbent candidate is too erratic. 
-Referring to Table 14-2, what is the numerical value of the center line for the p chart?
A) 0.53 
B) 0.56 
C) 0.63 
D) 0.66

Quizplus · Accepted Answer

The center line for a p chart is given by the overall proportion of successes.

Overall proportion of successes = (total number of voters favoring the incumbent) / (total number of voters surveyed)

From the table, we have:

Total number of voters surveyed = 100 x 8 = 800

Total number of voters favoring the incumbent = 430 + 460 + 500 + 520 + 480 + 470 + 540 + 490 = 3900

Overall proportion of successes = 3900 / 800 = 0.4875

Thus, the numerical value of the center line for the p chart is rounded to 0.49, which corresponds to choice B (0.56 is incorrect because it is the value for the upper control limit).

TABLE 14-2 A Political Pollster Randomly Selects a Sample of 100 Voters