/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 53 The following data represent the... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

The following data represent the total points scored in each of the NFL Super Bowl games played from 2001 through 2012 , in that order: \(\begin{array}{lllllllllll}41 & 37 & 69 & 61 & 45 & 31 & 46 & 31 & 50 & 48 & 56 & 38\end{array}\) Compute the range, variance, and standard deviation for these data.

Short Answer

Expert verified
The range of the scores is 38, the variance is approximately 118.139, and the standard deviation is approximately 10.868.

Step by step solution

01

Compute the range

The range is computed by subtracting the smallest value from the largest value in the data set. From the data set, we can see that the smallest value is 31 and the largest value is 69. Thus, Range = \(69 - 31 = 38\).
02

Compute the mean

The mean is computed by adding all the values in the data set, and dividing by the total number of values. So, Mean = \(\frac{41 + 37 + 69 + 61 + 45 + 31 + 46 + 31 + 50 + 48 + 56 + 38 }{12} \approx 46.417\)
03

Compute the variance

The variance is computed by taking each difference from the mean, squaring each difference, summing all the square differences, then dividing by the total number of values. Variance = \(\frac{(41-46.417)^2 + (37-46.417)^2 + (69-46.417)^2 + (61-46.417)^2 + (45-46.417)^2 + (31-46.417)^2 + (46-46.417)^2 + (31-46.417)^2 + (50-46.417)^2 + (48-46.417)^2 + (56-46.417)^2 + (38-46.417)^2 }{12} \approx 118.139\)
04

Compute the standard deviation

The standard deviation is computed by taking the square root of the variance. Standard deviation = \(\sqrt{118.139} \approx 10.868\)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Range
The range is a simple yet powerful concept in descriptive statistics. It's all about identifying how spread out a data set is. To find the range, you need to subtract the smallest value in the data set from the largest value. This gives you a quick glance at the dispersion of the data.

In the context of Super Bowl scores, the range tells us how dramatically scores can vary from one game to another. If the range is large, it means there were games with very different numbers of total points scored.

Consider our example data set, with scores ranging from 31 to 69 points. By calculating the range as 69 minus 31, we find the range to be 38. This means that across these games, the points scored spread over 38 points, highlighting variability within these games.
Variance
Variance offers a deeper insight into the data set by indicating how far each data point typically is from the mean. While range provides a single number describing data spread, variance examines each value's contribution to dispersion.

Calculating variance involves several steps:
  • Find the mean (average) of the data.
  • Subtract the mean from each data point to find the deviation of each point.
  • Square each deviation to eliminate negative signs and emphasize larger discrepancies.
  • Average these squared deviations.


For our Super Bowl scores, the mean score is about 46.417. For each game, we calculate how that score deviates from this mean and square it. After summing all these squared deviations and dividing by the number of games, we get the variance, approximately 118.139. This number tells us about the overall variability of scores around the average game score.
Standard Deviation
Standard deviation is like a close relative to variance. However, it is often more intuitive because it is expressed in the same unit as the data, unlike variance which is in squared units.

To find the standard deviation, simply take the square root of the variance. By doing this, you bring the value back to the original unit of the data, making it much more interpretable.

In the case of the Super Bowl scores from 2001 to 2012, with a variance of approximately 118.139, the standard deviation is about 10.868. This means that, on average, each game's score deviates from the mean score by around 10.868 points.

In summary, while variance provides a mathematical average of squared deviations, standard deviation offers a practical sense of how spread out the scores really are, relative to their average. This can help in understanding the consistency of performance across these games.

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Most popular questions from this chapter

A large population has a mean of 230 and a standard deviation of 41 . Using Chebyshev's theorem, find at least what percentage of the observations fall in the intervals \(\mu \pm 2 \sigma, \mu \pm 2.5 \sigma\), and \(\mu \pm 3 \sigma\).

The following data give the numbers of new cars sold at a dealership during a 20-day period. \(\begin{array}{rrrrrrrrrr}8 & 5 & 12 & 3 & 9 & 10 & 6 & 12 & 8 & 8 \\ 4 & 16 & 10 & 11 & 7 & 7 & 3 & 5 & 9 & 11\end{array}\) Make a box-and-whisker plot. Comment on the skewness of these data.

One disadvantage of the standard deviation as a measure of dispersion is that it is a measure of absolute variability and not of relative variability. Sometimes we may need to compare the variability of two different data sets that have different units of measurement. The coefficient of variation is one such measure. The coefficient of variation, denoted by CV, expresses standard deviation as a percentage of the mean and is computed as follows: For population data: \(\mathrm{CV}=\frac{\sigma}{\mu} \times 100 \%\) For sample data: $$ \mathrm{CV}=\frac{s}{\bar{x}} \times 100 \% $$ The yearly salaries of all employees who work for a company have a mean of \(\$ 62,350\) and a standard deviation of \(\$ 6820\). The years of experience for the same employees have a mean of 15 years and a standard deviation of 2 years. Is the relative variation in the salaries larger or smaller than that in years of experience for these employees?

The following stem-and-leaf diagram gives the distances (in thousands of miles) driven during the past year by a sample of drivers in a city. $$ \begin{array}{l|llllll} 0 & 3 & 6 & 9 & & & \\ 1 & 2 & 8 & 5 & 1 & 0 & 5 \\ 2 & 5 & 1 & 6 & & & \\ 3 & 8 & & & & & \\ 4 & 1 & & & & & \\ 5 & & & & & & \\ 6 & 2 & & & & \end{array} $$ a. Compute the sample mean, median, and mode for the data on distances driven. b. Compute the range, variance, and standard deviation for these data. c. Compute the first and third quartiles. d. Compute the interquartile range. Describe what properties the interquartile range has. When would the IQR be preferable to using the standard deviation when measuring variation?

The following data give the numbers of computer keyboards assembled at the Twentieth Century Electronics Company for a sample of 25 days. \(\begin{array}{llllllllll}45 & 52 & 48 & 41 & 56 & 46 & 44 & 42 & 48 & 53 \\\ 51 & 53 & 51 & 48 & 46 & 43 & 52 & 50 & 54 & 47 \\ 44 & 47 & 50 & 49 & 52 & & & & & \end{array}\) Prepare a box-and-whisker plot. Comment on the skewness of these data.

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