At an intersection, the red light times are normally distributed with a mean time of 3 minutes and a standard deviation of 0.25 minutes. Approximately what percent of red lights last between 2.5 and 3.5 minutes?

Question

campbell_st · Answer

2.5 mins is 2 standard deviations below the mean and 3.5 mins is 2 standard deviations above the mean. 

do you know the percentages...?

anonymous · Answer

no 
like the answers ?

campbell_st · Answer

ok... here is a google image of the normal curve with percentages add the percentages from -2 to + 2 http://www.google.com.au/imgres?imgurl=&imgrefurl=http%3A%2F%2Fhistoriesofcatastrophicdreaming.wordpress.com%2Fquantitative-methods%2Fsecond-exam-qm%2Fnormal-distributions-and-the-rule-of-68-95-99%2F&h=0&w=0&sz=1&tbnid=xSUu-Iww1YWzaM&tbnh=177&tbnw=285&zoom=1&docid=eYdbGhkH-DvCoM&hl=en&ei=DB45Us7JBs-DkgX_6YHAAQ&ved=0CAIQsCU