During flu season, a city medical center needs to keep a large supply of flu shots. A nurse’s aid compiles data on the number of flu shots given per day in the past few years during flu season. A cumulative probability chart of the collected data is as follows:

How many flu shots should the center store every day to meet the demand on 95 percent of the days?

(A) |
At most 190 |

(B) |
At most 140 |

(C) |
Exactly 170 |

(D) |
At least 150 |

(E) |
At least 200 |

Correct Answer: E

Explanation:

E Look closely at the chart. For example, the point (160, 0.4) indicates that on 40 percent of the days, up to 160 shots were given. To find the number of shots needed to meet the demand on 95 percent of the days, we need to find the 95th percentile. Draw a horizontal line from the cumulative probability of 0.95 to the curve. From the point at which the line meets the curve, draw a vertical line down to the x-axis, and then read the number of flu shots given there. It should be approximately 200.