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STATISTICS 2005

Fundamentals of Statistics Section 95

TI-83 Instructions

Calculating means and standard deviations from frequency tables

Relative Frequency Histograms

Instructor: Pete Wildman

Fall Semester 1999

Frequency tables on the TI-83 calculator - calculating means and drawing relative frequency histograms

 You can think of this as an advanced topic - but if you master it, you can save a great deal of time and effort!

Suppose you have the following speeding ticket data

Speed of drivers who received speeding tickets in a 30 m.p.h. zone

Classes

Frequency

42-43

14

44-45

11

46-47

8

48-49

6

50-51

4

52-53

3

54-55

1

56-57

2

58-59

0

60-61

1

Here is one way to input this data in the list of calculators

  1. Clear out lists L1 through L5 or save the data in these lists in another location
  2. Enter the lower class limits in L1
  3. Enter the upper class limits in L2
  4. Enter the frequency in L3

Here are what your screens should look like after each of these operations:

Enter lower class limits in L1

Enter upper class limits in L2

Enter Frequencies

Now use the arrow keys to highlight L4 and enter ( L1 + L2) / 2. Your screen should look like the picture below:

Now hit enter and you will have the class marks in L4. Your screen should be like the drawing given below

Now quit the editor (2nd MODE) and return to the homescreen. Hit STAT CALC 1, this should give you the expression below:

Now type in L4 (this is where the class marks are located) a comma and finally L3 (this is where the frequencies are located. Note it is very important to list the list with the class marks first followed by the list with frequencies. Your screen should look as follows

Now hit enter and you will get the value for the estimated mean

Relative Frequency Histograms

Since you have the frequency table in your calculator - it is easy to get a relative frequency histogram from your current set up. Do the following

  1. Return to the STAT editor
  2. Use the arrow keys to highlight the list L5
  3. Type in L3 , the divide key, 2nd STAT (for the list menu), left arrow (for math submenu), 5 (for sum), L3 and a closing parenthesis. These last steps are shown below

Return to editor and highlight L5

Enter L3

Enter divide

Enter 2nd STAT

(your screen may differ)

Left arrow for Math menu

Enter 5 for sum

Enter L3

Enter ) and hit enter

You now have the relative frequencies in L5. So now set up your STAT PLOT menu for histograms - but with an important difference! Make Xlist the class marks (in this case L4) and Freq the frequencies (in this case L3). Here is what your screen should look like:

 

Now set the window. Here are ones appropriate for this histogram

Now hit GRAPH and TRACE to get the relative frequency histogram