Starter: After selling Lotto tickets for 5 years, an agent knows that weekly sales are normally distributed with a mean of $3500 and a standard deviation of $650. What level of weekly sales would the agent exceed 85% of the time? A salesman travels between Whanganui and Wellington daily. His time for the journey is normally distributed with a mean of 2 hours and 45 minutes (165 minutes) and a standard deviation of 8.0 minutes. What percentage of his trips take: a)Longer than 3 hours b)Less than 2 hours and 43 minutes c)Between 2 hours 30 minutes and 2 hours 40 minutes P(X > 180) = = 3% P(X < 163 ) = = 40% P(150 < X < 160 ) = = 23.6% $2826

Note 12: RISK When an event is viewed in a negative way then its probability of occurring maybe referred to as a risk Relative Risk Used to compare the risk (probability) of an event for one group with the risk (probability) of an event for another The risk for the second group may be referred to as the base-line risk. Relative risk = probability of variable present probability of variable not being present

Example: Students were asked to tick a box indicating whether the time they had spent preparing for an assessment was less than 3hr or at least 3hrs – the results are: 1.Calculate the risk of not achieving 2.Calculate the risk for not achieving for students with less than 3hrs preparation 2.The risk for not achieving with at least 3 hours preparation < 3hrs> 3hrs Total Achieved Not Achieved Total / / / 177

Example: Students were asked to tick a box indicating whether the time they had spent preparing for an assessment was less than 3hr or at least 3hrs – the results are: 4.Calculate the Relative Risk for not achieving students with less than 3hrs prep compared to not achieved for students that prepared for more than 3hrs < 3hrs> 3hrs Total Achieved Not Achieved Total / / 177 = 1.32 A student who studied for 3 hours

Workbook Page 171 Exercise C Workbook Page 171 Exercise C