3.2 measures of variability
DESCRIPTION
3.2 Measures of Variability. Objectives: By the end of this section, I will be able to… Understand and calculate the range of a data set. Explain in my own words what a deviation is. Calculate the variance and the standard deviation for a population or a sample. What is variation ?. - PowerPoint PPT PresentationTRANSCRIPT
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3.2 Measures of Variability
Objectives:By the end of this section, I will beable to…
1) Understand and calculate the range of a data set.
2) Explain in my own words what a deviation is.
3) Calculate the variance and the standard deviation for a population or a sample.
![Page 3: 3.2 Measures of Variability](https://reader036.vdocuments.site/reader036/viewer/2022062309/568152db550346895dc0f866/html5/thumbnails/3.jpg)
What is variation?
It is the spread of the
numbers around the
mean.
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Measures of Variation
1. Variance
2. Standard Deviation
3. Range
22 ( )
1
x xs s
n
22 ( )
1
x xs
n
Highest – Lowest
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Why is VARIATION important?
Because less variation means smaller
spread in the data, which means
1. More precise estimates
2. Higher confidence in our
conclusions about the data
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Wall Street Journal competition
Stocks were chosen by1. Journal staff randomly throwing darts
at a list of the stocks2. A team of four financial experts3. The DJIA (Dow Jones Industrial
Average)
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THE RESULTS ARE…
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Variations and Graphs
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Measuring V-Span
1. Make a V between your index finger and your middle finger when you spread them as far as possible.
2. Measure to the nearest tenth of a centimeter.
Your V-Span =
3. Compute the group’s mean V-Span.
Mean V-Span =
4. Now fill out the following chart with your data and find the three values of variation
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x x-mean (x-mean)2
Variance =
Sum/(n – 1)
Put in all of your V-spans as x values. Add rows as necessary.
Then use the mean (average V-span) and find the difference between each x value and the mean
Square the number you just found…
Standard deviation = Square ROOT of the variance
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Calculator Time
Find the variance and standard deviation on your calculator.
![Page 12: 3.2 Measures of Variability](https://reader036.vdocuments.site/reader036/viewer/2022062309/568152db550346895dc0f866/html5/thumbnails/12.jpg)
NASCAR TIME - link
On a separate sheet of paper, and one per person – NEATLY complete the following.
Find the mean, median, mode, range, variance, and standard deviation of NASCAR points of the top 10 drivers for 2010.