statistics 216 Exam 1

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statistics 216 Exam 1
2014-02-26 23:33:06

stats 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