The radio music listener market is diverse listener formats might include adult call temporary ,album rock,top 40 oldest,rap country and western classical and jazzy in targeting audiences market researchers need to be concerned about the ages of the listeners attracted to particular formats.suppose a market researchers surveyed a sample of 170 listeners of country music radio stations and obtained the following age distribution.

Age 15 under 20 frequency 9,20 under 25 , 16,25 under 30,27 30 under 35 44,35 under 40 42,40 under 45 23, 45 under 50 7 and 50 under 55 2.

What are the mean,median and modal ages of country music listener.

What is the variance and standard deviation?