statistics 216 Exam 1
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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
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
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
What is the % rule for the normal model of standard deviation
68 - 95 - 99.7 Rule
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)
What does the invnorm calculator function used for?
- Can find z-scores in reverse
- find a certain percentile
- invnorm (proportion, mean, standard deviation)
how can you find the IQR using a normal standard deviation model?
Take the 25th percentile - the 75th percentile
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
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
When do you use a scatter plot?
When you want to determine the relationship between QUANTITATIVE variables
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