# statistics 216 Exam 1

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1. What are Z-scores and what do they tell you? and what is the formula?
• Standardize scores and they tell you how many standard deviations above or below the mean a score is.
• The formula is:  (score - mean)/ Standard deviation
2. what does shifting do to z-scores
• adding or subtracting a constant from every date value
• the 5-number summary - increased by the constant
• median - increased by constant
• mean - increased by constant
• IQR - stays the same
• Standard deviation - stays the same
3. What does rescaling do to z-scores
• multiplying or dividing all the values by a constant
• 5 # summary: mult. or divide by constant
• Median: mult. or divide by constant
• Mean: mult. or divide by constant
• IQR:  mult or divide by constant
• Standard deviation:  Multiplied or divide by constant
4. What is the % rule for the normal model of standard deviation
68 - 95 - 99.7 Rule
5. What does normalcdf function on the calculator do and how do you use it?
• calculates area under a normal curv
• normalcdf( start, end, mean, standard deviation)
6. What does the invnorm calculator function used for?
• Can find z-scores in reverse
• find a certain percentile
• invnorm (proportion, mean, standard deviation)
7. how can you find the IQR using a normal standard deviation model?
Take the 25th percentile - the 75th percentile
8. With scatter plots what variable do you put on the x-axis and what one on the y-axis
• the explanatory variable goes on the x-axis
• the responsive variable goes on the y-axis
9. What is the correlation
the measure of the strength of the linear association

It is very sensitive to outliers

The more association the closer to 1 the correlation will be
10. When do you use a scatter plot?
When you want to determine the relationship between QUANTITATIVE variables
 Author: macylynn92 ID: 263971 Card Set: statistics 216 Exam 1 Updated: 2014-02-27 04:33:06 Tags: stats Folders: Description: stats exam 1 Show Answers: