Practice
OK, now it's time to think like a statistician!
Here's a summary of formulas that we've encountered.
Sample variance: s2 = Σ(X-M)2/ (n-1)
(where X is the individual score, M is the mean, and n is the sample size)
Standard deviation: = s = √Σ(X-M)2/ (n-1)
z-score transformation: z = X - M / s
(where X is the individual score, M is the mean, and s is the standard deviation)
Practice:
You and your friends have just measured the heights of your dogs (in millimeters):
The heights (at the shoulders) are: 600mm, 470mm, 170mm, 430mm and 300mm.
Challenge
Find the mean for the dogs' heights.
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Challenge
Find the sample variance for the dogs' heights.
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Challenge
Find the standard deviation of the sample of dogs' heights.
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Challenge
The patient recovery time from a particular surgical procedure is normally distributed with a mean of 5.3 days and a standard deviation of 2.1 days. What is the z-score for a patient who takes 10 days to recover?
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Challenge
A racecar track records the times of each racecar driving a mile on the track. The times were recorded in seconds: 59.4, 48.7, 45.0, 56.1, 60.1, 49.8 Find the standard deviation for this sample set.
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