Stats Exam Cheat Sheet

# Stats Exam Cheat Sheet - -Areas of rectangles=relative...

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Unformatted text preview: -Areas of rectangles=relative frequencies, the height=density (% / horiz.unit); Area= base x height (all must add to 100%) To Draw: make frequency/relative frequency table, use appropriate intervals on the x axis, and record the heights at the top of each drawn rectangle-68, 95, 99.7 rule; Use Root-Mean-Square to find SD ; Effects on Avg and SD of adding a constant to every number, multiplying by a constant- Standard Units (z) = (Value-Avg)/SD; Percentiles- “to the left”, use symmetry! Plotting Points (x,y); -X goes over, Y goes up and down; Slope = rise over run (positive or negative); y = m( x )+b; Find b (y intercept) Correlation Coefficient and SD Line-Averages of X and Y make point of averages; The coefficient, r , is between -1 and 1-SD line goes through the point of averages, slope is (SD of y )/ (SD of x )-To calculate r , convert each variable to standard units, find products, take average.-Equation of the line for y on x estimates the average value of y for each x-For each increase of 1 SD on x , there is an incr. of r SDs on y , on average-Regression Method for individuals vs. groups-“Regression Effect”- as scatter spreads out, an increase in one and decrease in the other are often offsetting and misleading-“Regression Fallacy”- thinking that there is more to be interpreted-Equation for Reg. Line goes thru the Pt of Avg; Slope=rise over run- if our run is 1 SD x , our rise is r (SD y )- m= -y = m x +b, write out the final equation-Opposite rule P(event) = 1- P(opposite event) Key words “at least one”-Mult Rule- The chance that 2 things will both happen=chance the 1 st will happen x the chance the 2 nd will happen given the first will happen. will happen given the first will happen....
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Stats Exam Cheat Sheet - -Areas of rectangles=relative...

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