For the following set of data, find the percentage of data within 2 population standard deviations of the mean, to the nearest percent.\begin{tabular}{|c|c|}\hline Data & Frequency \\\hline 6 & 2 \\\hline 9 & 7 \\\hline 10 & 10 \\\hline 11 & 14 \\\hline 15 & 18 \\\hline 16 & 15 \\\hline 18 & 9 \\\hline 19 & 8 \\\hline 20 & 1 \\\hline\end{tabular}
Q. For the following set of data, find the percentage of data within 2 population standard deviations of the mean, to the nearest percent.\begin{tabular}{|c|c|}\hline Data & Frequency \\\hline 6 & 2 \\\hline 9 & 7 \\\hline 10 & 10 \\\hline 11 & 14 \\\hline 15 & 18 \\\hline 16 & 15 \\\hline 18 & 9 \\\hline 19 & 8 \\\hline 20 & 1 \\\hline\end{tabular}
Calculate Mean: Calculate the mean of the data set.Mean = (Sum of all values)/(Total number of values)= (6×2+9×7+10×10+11×14+15×18+16×15+18×9+19×8+20×1)/(2+7+10+14+18+15+9+8+1)= (12+63+100+154+270+240+162+152+20)/84= 1073/84= 12.77 (rounded to two decimal places)
Calculate Standard Deviation: Calculate the standard deviation of the data set.First, find the variance by using the formula: Variance = Total number of valuesSum of (value−mean)2×frequencyVariance = 84(6−12.77)2×2+(9−12.77)2×7+(10−12.77)2×10+(11−12.77)2×14+(15−12.77)2×18+(16−12.77)2×15+(18−12.77)2×9+(19−12.77)2×8+(20−12.77)2×1= 84(−6.77)2×2+(−3.77)2×7+(−2.77)2×10+(−1.77)2×14+(2.23)2×18+(3.23)2×15+(5.23)2×9+(6.23)2×8+(7.23)2×1= 8491.5729×2+14.2129×7+7.6729×10+3.1329×14+4.9729×18+10.4329×15+27.3529×9+38.8129×8+52.2729×1= 84183.1458+99.4903+76.729+43.8606+89.5112+156.4935+246.1761+310.5032+52.2729= 841258.1826= 14.9786 (rounded to four decimal places)Standard deviation = Variance= 14.9786= 3.87 (rounded to two decimal places)
Determine Range: Determine the range within 2 standard deviations of the mean.Lower bound = Mean - 2× Standard deviation=12.77−2×3.87=12.77−7.74=5.03 (rounded to two decimal places)Upper bound = Mean + 2× Standard deviation=12.77+2×3.87=12.77+7.74=20.51 (rounded to two decimal places)
Count Values in Range: Count the number of values within the range of 5.03 to 20.51. Values within range: 6, 9, 10, 11, 15, 16, 18, 19 (20.510 is slightly outside the range) Frequency within range: 20.511
Calculate Percentage: Calculate the percentage of values within 2 standard deviations.Percentage = (Total number of valuesFrequency within range)×100= (8483)×100= 98.81\% (rounded to nearest percent)
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