AP Stats Quiz Study

Categorical Data

  • Associated = Not Independent

  • Not Associated = Independent

    • You find out if two variables are associated by a comparison; showing that at least 2 probabilities are equal or unequal

    • Check if percentage distribution of one variable stays the same across all other categories of the other variable on a frequency table


Quantitative Data

  • CSOCS

    • C = Context

      • Sprinkle in context throughout, including units of measurement

    • S = Shape

      • Ex: normal, skewed left, skewed right, bimodal, unimodal, symmetrical, etc. Use terms like roughly or approximately

    • O = Outliers

      • If there arenā€™t any outliers, donā€™t mention any. Also discuss unusual features like gaps on a histogram

    • C = Center

      • Approximate the mean or median

    • S = Spread

      • Can approximate the range or IQR. Donā€™t use range as a noun; use range of values or calculate the actual range (max value - min value)

  • Checking for Outliers

    • Q1 is the median of the lower half of the value set

    • Q3 is the median of the upper half of the value set

    • IQR = Q3-Q1

    • Lower Fence = Q1 - 1.5xIQR

    • Upper Fence = Q3 + 1.5xIQR

  • Standard Deviation

    • What is it? How spread out the numbers of a data set are from the mean

      • Low standard deviation = Numbers are clustered closely around average

      • High standard deviation = Numbers are spread out over a wide range of values

        • How to find

          • Step 1: Subtract the mean from each score to find the deviation

          • Step 2: Square each deviation value to find the squared deviation

          • Step 3: Add all of the squared deviations together

          • Step 4: Divide by sample size (n) minus 1 to find the variance, sĀ²

          • Step 4: Take the square root of the variance to find the Standard Deviation, s

        • Template for interpreting standard deviation on a set of data

          • ā€œOn average, a randomly-selected [context] will be [SD units] away from the mean of [mean units]


How to Display Quantitative Data

  • Boxplots

    • Outliers are shown as individual dots

    • Box ranges from Q1 to Q3, the line goes where the median is

    • The whisker ranges from the lower fence to the last non-outlier value outside of the fence, not the upper fence

  • Stemplot

    • Sort data points from smallest to largest. Split each number into two parts: the first digit on the right and the remaining digits to the left

    • Ex: If there is a value of 42, the stem is 4 and the leaf is 2. 4|2

    • Example Stemplot:

      • Values: 43, 42, 45, 68, 54, 63, 72, 89, 88, 91

      • 4 | 2 3 5

      • 5 | 4

      • 6 | 3 8

      • 7 | 2

      • 8 | 8 9

      • 9 | 1

  • Calculator Magic to find Q3, Q1, Median

    • STAT

    • Edit

    • L1, L2

    • Stat

    • Calculate

    • 1-var stat

    • List = L1, Frequency List = L2

    • Calculate