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The following are the ages in years of 40 stds who went on an excursion 12,13,14,12,15,14,13,16,14,15,13,14,14,15,16,12,13,14,15,15,15,13,12,15,16,14,15,15,


The following are the ages in years of 40 stds who went on an excursion

12,13,14,12,15,14,13,16,14,15,13,14,14,15,16,12,13,14,15,15,15,13,12,15,16,14,15,15,

13,14,12,13,15,15,16,16,12,14,15,14,

a) Draw up a frequency table and state the modal age

b)calculate the arithmetic mean of all the ages to the nearest month
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2 Answers

Hi Christopher,
 
A frequency table simply lists the number of times a certain event occurs, usually by keeping a tally. I will try my best to represent it here:
 
a)  Age      Tally           Frequency
 
      12       ||||||                6
      13       |||||||               7
      14       ||||||||||          10
      15       ||||||||||||       12
      16       |||||                  5
 
The mode is simply the value that appears the most often in a data set. Since "15" occurs the greatest amount of times, 12 times to be exact, this is the modal age.
 
b) The arithmetic mean is the sum of every age divided by the number of students, in this case 40 [ie. (12+12+12+12+12+12+13+13+13+13+...+16+16+16+16+16)/40]
 
Carrying out this calculation to completion gives you 563/40, which is equal to 14.075. Since the problem asks the mean to the nearest month, you would multiply 0.075*12(months in the year), which gives you 0.9. Rounding up to the nearest month results in an arithmetic mean of 14 years, 1 month.
 
As you can see, the mode and the mean represent two different statistical characteristics of a data set, although they are quite close to one another. The mean is more affected by outliers than the mode, so the amount of students aged 12 and 13 reduce the average age.

Finally, a third way to represent the data (not asked for here), is the median. To arrive at the median, you would write out every age from youngest to oldest, and find the value in the middle; if there are two values (in an even-numbered data set), you would average these two values to get the median.
 
Hope this helps!
 
-Jason
 
Christopher,
 
A frequency table is pretty straightforward.  It's simply the ages and the number of times that age occurs in the data provided. 
 
12     6
13     7
14     10
 
etc.
 
 
The modal age is the age that has the highest count.  (15, if I counted right).
 
The arithmetic mean is the sum of the ages divided by 40.  This will give you a decimal value for years.  E.g. 14.06 years.  To convert this to years and months, drop the whole number and multiple the decimal times 12.  This will give you the remainder in months so that you can round to the nearest month. 
 
14.06 years
Drop the 14, multiply .06 and 12 = .72 months
so the average age to the nearest month is 14 years, 1 month.
(Emphasis, this is an example, not the solution)