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Figure 7-18. Visualization of the survey results
The chief statistician explained to him the concept of sample statistics and population para-
meters, the central limit theorem, and binomial proportion confidence intervals. The survey
was not unlike flipping coins—the possibilities were two-fold: either a student was in chess
club, or not. Given a certain number of students surveyed, it was possible to compute an in-
terval for each city and grade at a certain degree of confidence.
The statistician used the normal approximation interval formula to put error bars around each
proportion.
To do so, he first needed to create a parameter that allowed the president to select his desired
degree of confidence, as shown in
Figure 7-19
.
