Chapter 3 Flashcards
3 main “measures of center”
- Mean
- Median
- Mode
Mean
Obtained by dividing the sum of all values by the number of values in the data set.
Median
The value that divides a data set that has been sorted in increasing order into two equal halves.
Mode
The value that occurs w/ the highest frequency in a data set.
Mean for population data
u = sum on all x’s / N
Mean for sample data
X bar = sum of all x’s /n
2 steps to calculate the median
- Sort the data set into increasing order
- Find the value that divides the sorted data set in two equal parts.
Can there be no mode?
Yes
Can modes be from qualitative data?
Yes
Can there be more than one mode?
Yes
What are the mean, median, and mode of a symmetrical histogram /distribution curve
Mean = median = mode
Mean, median, and mode of a right-skewed histogram
Mean > median > mode
Left-skewed histogram mean, median, and mode
Mean < median < mode
Trimmed mean
After we drop K% of the values from each end of a ranked data set, the mean of the remaining values is called the K% trimmed mean.
Weighted mean
When each value of a data set is assigned a different weight.
Sum of x* W/ sum of W
Measures of dispersion tell us…
How much variation exists around that “typical value”