Journal Prompt

Frequency Table to Organize & Display Data D. Otap – Spring Semester 2015

Frequency The number of times a data term occurs Example: How many times does each number appear? 1, 2, 3, 3, 4, 5, 5, 5, 6

Distribution The distribution of a variable gives:  Possible values of the variable  Relative frequency of each value

Range The range is the: distance between the lowest and highest values Range = Maximum - Minimum

Frequency Table A frequency table:  Shows the number of times a data value occurs  Summarizes data We can use frequency tables to make comparisons, predictions and inferences.

Creating a Frequency Table Draw a table with 3 columns  Column 1 – Values or Intervals  Column 2 – Tally the results  Column 3 – Totals IntervalTallyTotal

 Column 1 – Values or Intervals o Choose a range that includes all of the data Make sure the range includes: the lowest value (minimum) the highest value (maximum) o For grouped data intervals should be equal Column 1 – Intervals

 Interval size - determined by the range in data values If range in data values is small, intervals will be small If range in data values is large, intervals will be large  Intervals must be of equal size  Intervals Cannot Overlap

Pay Attention to Details! The example gives the wrong lower extreme. It should be: Lower Extreme = 12.1 Upper Extreme = 25.9 Range = 25.9 – 12.1 = 13.8

12.1

Column 2 - Tally  Column 2 – Tally the results o Use a tick mark to represent each time the data occurs (hint: lightly cross off the data as you use it)

IntervalTallyFrequency 10 – – – – 29.9

Column 3 – Totals  Column 3 – Totals o Count the tally marks to determine the frequency and write the total

IntervalTallyFrequency 10 – – – –

Example - Sleep. 20 people were asked to state the average number of hours they sleep each night. Results of the survey: 7, 8, 6, 9, 10, 12, 5, 7, 8, 9, 10, 11, 12, 7, 6, 7, 8, 10, 11, 9

Example 2 - continued 7, 8, 6, 9, 10, 12, 5, 7, 8, 9, 10, 11, 12, 7, 6, 7, 8, 10, 11, 9 Step 1: Make a table with three columns. Intervals Tallied results Frequency results The range is not wide so use an interval of 1

Step 2: Tally the data Step 3: Count tally marks to get frequency 7, 8, 6, 9, 10, 12, 5, 7, 8, 9, 10, 11, 12, 7, 6, 7, 8, 10, 11, 9 IntervalsTallyFrequency IntervalsTallyFrequency 5 – 6 7 – 8 9 –