Date post: | 01-Jan-2016 |
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Measures of Central Tendency are…
Mean - average Median – the middle number Mode – the number that is there the
most
Measures of Variability
Tell you how far apart or how spread out the data is Range = biggest – smallest Interquartile range (IQR) = Q3 – Q1 (the
middle 50% of the data) Variance Standard Deviation
Formulas
We will now be writing the mean with a new formula
xx
n
X bar means “mean” sum
Numberof terms
Mean is the average
To find the mean of the high temperatures in a week which are:
80, 78, 81, 83, 76, 82, and 801st Add all the numbers2nd Count all the numbers you have.3rd Divide the total by the
number of numbers that you have.
Median is the middle number
To find the median of the high temperatures in a week, which were:
80, 78, 81, 83, 76, 82, and 801st Write the numbers in order from
smallest to largest.2nd Count the numbers and find the
middle one. If you have an even number, then average the two middle numbers.
Mode is the most frequently occurring number
To find the mode of the high temperatures in a week, which were:
80, 78, 81, 83, 76, 82, and 801st Write the numbers in order from smallest to largest.2nd Look for the number that appears the most number of times.
To Make a box and whisker plot:
2nd Find the lower and upper extreme. 76 78 80 80 81 82 83
3rd Draw a number line that has scale greater than the range of the given numbers.
8476 77 81807978 82 83
To Make a box and whisker plot:
3rd Put the points above the number line at the lower extreme, the lower quartile, the median, the upper quartile, and the upper extreme.
76 77 81807978 82 83
To Make a box and whisker plot:
4th Draw a box around the lower and upper quartiles and a vertical line through the box where the median is located.
76 77 81807978 82 83
To Make a box and whisker plot:
5th Run whiskers from the box to the lower and upper extreme.
76 77 81807978 82 83
Steps to calculate variance
Find the mean Subtract each data point from the
mean Square each of these numbers Add these all up Divide by the number of terms Making a table is helpful!