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A teacher was looking through her grade book at her students' test scores. Which score in the data set would be considered an outlier?





Test Scores


87
78
90
81
100


93
82
87
45
74




A 45
B 74
C 78
D 81

33. A teacher was looking through her grade book at her students' test scores. Which score in the data set would be considered an outlier?\newline\begin{tabular}{|c|c|c|c|c|}\newline\hline \multicolumn{55}{|c|}{ Test Scores } \\\newline\hline 8787 & 7878 & 9090 & 8181 & 100100 \\\newline\hline 9393 & 8282 & 8787 & 4545 & 7474 \\\newline\hline\newline\end{tabular}\newlineA 4545\newlineB 7474\newlineC 7878\newlineD 8181

Full solution

Q. 33. A teacher was looking through her grade book at her students' test scores. Which score in the data set would be considered an outlier?\newline\begin{tabular}{|c|c|c|c|c|}\newline\hline \multicolumn{55}{|c|}{ Test Scores } \\\newline\hline 8787 & 7878 & 9090 & 8181 & 100100 \\\newline\hline 9393 & 8282 & 8787 & 4545 & 7474 \\\newline\hline\newline\end{tabular}\newlineA 4545\newlineB 7474\newlineC 7878\newlineD 8181
  1. List test scores: List all the test scores in ascending order. 45,74,78,81,82,87,87,90,93,10045, 74, 78, 81, 82, 87, 87, 90, 93, 100
  2. Calculate IQR: Calculate the interquartile range (IQR).\newlineFirst, find the median, which is the average of the 55th and 66th scores: (82+87)/2=84.5(82 + 87) / 2 = 84.5\newlineThen, find the medians of the first half and the second half to get Q1Q1 and Q3Q3.\newlineFirst half: 45,74,78,81,8245, 74, 78, 81, 82. Median (Q1Q1) is 7878.\newlineSecond half: 87,87,90,93,10087, 87, 90, 93, 100. Median (Q3Q3) is 9090.\newlineIQR=Q3Q1=9078=12IQR = Q3 - Q1 = 90 - 78 = 12
  3. Determine outlier boundaries: Determine the outlier boundaries.\newlineLower boundary = Q11.5×IQR=781.5×12=7818=60Q1 - 1.5 \times IQR = 78 - 1.5 \times 12 = 78 - 18 = 60\newlineUpper boundary = Q3+1.5×IQR=90+1.5×12=90+18=108Q3 + 1.5 \times IQR = 90 + 1.5 \times 12 = 90 + 18 = 108
  4. Identify outliers: Identify any scores outside the boundaries.\newlineThe score of 4545 is below the lower boundary of 6060, so it's an outlier.

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