




Last updated at Aug. 25, 2021 by Teachoo
Example 5 The record of a weather station shows that out of the past 250 consecutive days, its weather forecasts were correct 175 times. (i) What is the probability that on a given day it was correct? The total number of days for which the record is available = 250 Number of days when forecast was correct = 175 P(the forecast was correct on a given day) = (ππ’ππππ ππ πππ¦π πππ π€βππ πππππππ π‘ π€ππ πππππππ‘)/(πππ‘ππ ππ’ππππ ππ πππ¦π πππ π€βππβ π‘βπ ππππππ ππ ππ£πππππππ) = 175/250 = 0.7 Example 5 (Method 1) The record of a weather station shows that out of the past 250 consecutive days, its weather forecasts were correct 175 times. (ii) What is the probability that it was not correct on a given day? The total number of days for which the record is available = 250 The number of days when the forecast was not correct = 250 β 175 = 75 P(the forecast was not correct on a given day) = (ππ’ππππ ππ πππ¦π πππ π€βππ πππππππ π‘ π€ππ πππ‘ πππππππ‘)/(πππ‘ππ ππ’ππππ ππ πππ¦π πππ π€βππβ π‘βπ ππππππ ππ ππ£πππππππ) = 75/250 = 0.3 Example 5 (Method 2) The record of a weather station shows that out of the past 250 consecutive days, its weather forecasts were correct 175 times. (ii) What is the probability that it was not correct on a given day? P(the forecast was not correct on a given day) = 1 β P(forecast was correct on a given day) = 1 β 0.7 = 0.3