Chapter 16 Flashcards
(20 cards)
What is the equation for frequency density?
FD = Frequency/class width.
Define cumulative frequency.
Total number of data items less than or equal to a specific value.
If data is in bands what value do you use for a cum. freq. graph?
Upper bound.
What percentiles are the median, upper and lower quartiles?
50th, 75th and 25th.
When are box-and-whisker plots useful?
Comparing two sets of data.
How do stem-and-leaf diagrams work?
Rows according to first digit showing overall distribution. Only practical for data sets of moderately large size. Can compare two or find median/upper quartile.
What is standard deviation?
Measure of mean difference of each data point from the mean value.
What are the standard deviation formulas?
Look in book.
What is the variance?
Standard deviation squared.
How do you work out the mean of a frequency table?
Sum(fx)/n.
What is the formula for variance?
Sum(fx^2)/n - mean^2.
What is bivariate data?
Comes in pairs.
What does strong positive correlation mean?
As x increases so does y.
What does negative correlation mean?
As x decreases so does y.
What does no correlation mean?
x and y don’t have a clear relationship.
What is r?
Correlation coefficient - -1 to 1 (linear).
Why might there be correlation even if the two factors don’t affect each other?
Third factor.
What is another name for a line of best fit?
Regression line.
Why are numbers less valid when you extend the regression line?
Extrapolating data.
How do you find outliers?
Over 1.5 IQRs from the nearest quartile or over 2 standard deviations from the mean.
