Statistics · real student question

Fifteen children of low number-talk parents scored 2,1,2,3,4,3,3,2,2,1,5,3,4,1,2 and fifteen children of high number-talk parents scored 3,4,5,4,5,4,2,3,5,4,5,3,4,5,4. Complete a frequency distribution table for scores 1 to 5 in each group.

Question

Two groups of 1515 children were scored on knowledge of numbers.

Low number-talk parents: 2,1,2,3,4, 3,3,2,2,1, 5,3,4,1,22,1,2,3,4,\ 3,3,2,2,1,\ 5,3,4,1,2

High number-talk parents: 3,4,5,4,5, 4,2,3,5,4, 5,3,4,5,43,4,5,4,5,\ 4,2,3,5,4,\ 5,3,4,5,4

Complete the frequency distribution table giving flowf_{\text{low}} and fhighf_{\text{high}} for each score X=1,2,3,4,5X=1,2,3,4,5.

Step-by-step solution

  1. Set up the tally in a fixed order. List the possible scores 11 through 55 and pass through the data once, marking each value. Working score-by-score instead (scanning the list five times) is what usually causes a value to be counted twice or missed.

  2. Tally the low group. Going through 2,1,2,3,4,3,3,2,2,1,5,3,4,1,22,1,2,3,4,3,3,2,2,1,5,3,4,1,2:

    X=1X=1 appears at positions 22, 1010, 141433 times

    X=2X=2 appears at positions 1,3,8,9,151,3,8,9,1555 times

    X=3X=3 appears at positions 4,6,7,124,6,7,1244 times

    X=4X=4 appears at positions 5,135,1322 times

    X=5X=5 appears at position 111111 time

  3. Tally the high group. Going through 3,4,5,4,5,4,2,3,5,4,5,3,4,5,43,4,5,4,5,4,2,3,5,4,5,3,4,5,4:

    X=1X=100 times; X=2X=211 time; X=3X=333 times; X=4X=466 times; X=5X=555 times.

  4. Assemble the table.

    XXflowf_{\text{low}}fhighf_{\text{high}}
    515
    426
    343
    251
    130
    Total1515
  5. Check both columns against n. 1+2+4+5+3=151+2+4+5+3=15 ✓ and 5+6+3+1+0=155+6+3+1+0=15 ✓. This total is the essential check: a frequently circulated version of this table lists the low column as 1,2,3,5,41,2,3,5,4, which also sums to 1515 but swaps the counts of X=1X=1 and X=3X=3 — only re-tallying, not the total, catches that.

    flow: 3,5,4,2,1  (X=15);fhigh: 0,1,3,6,5\boxed{f_{\text{low}}:\ 3,5,4,2,1\ \ (X=1\ldots5);\qquad f_{\text{high}}:\ 0,1,3,6,5}

  6. Read the comparison the table is for. The low group piles up at scores 1122 (eight of fifteen children) while the high group piles up at 4455 (eleven of fifteen), so the distributions are shifted rather than merely differently spread — which is the point the original study was making.

Answer

flow=3,5,4,2,1 and fhigh=0,1,3,6,5 for X=1,2,3,4,5f_{\text{low}}=3,5,4,2,1\ \text{and}\ f_{\text{high}}=0,1,3,6,5\ \text{for}\ X=1,2,3,4,5

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