Term

Definition
subtract values from mean, square all the differences, add up all the differences, then divide by the number of observations 


Term

Definition
take sq root of variance. (subtract values from mean, square em, add em up, divide by # observations, take sq root) 


Term
steps for measures of assoc w/ 2 ordinal variables (K's gamma, Taub, Tauc, Somer's d) 

Definition
create frequency table w/ cells for totals. id the pairs which are concordant, discordant, tied on the row, tied on the column. For each type of pair (concordant, discordant, TR, TC), multiply the 2 #s together and add up all the products. For ex. (4 x 3) + (4 x 6)... 


Term

Definition
subtract values from mean, multiply differences for one variable by the the differences for the other variable, add products up, divide by # of observations (not the total number of the two variables added up, but just the number of pairs observations being compared) 


Term
how to calc std error for cont variables 

Definition
subtract mean from each of values, square em, add up squares, divide by # of observations minus 1, take sq root, then divide by sq root of the number of observations 


Term
twotailed vs onetailed hypothesis 

Definition
if population mean could be above or below the test value, it's twotailed. if the pop mean can only be above or only be below the test value, it's onetailed 


Term
when to use the different means tests  Ztest and paired Ttest 

Definition
use Ztest when trying to find out if a population mean is equal to a particular value. Paired ttest is used to test whether the mean of one variable is equal to the mean of another variable 


Term

Definition
specify the hypothesis that the population mean is/isnt equal to (the test value). Write down the alternative hypothesis and whether it's onetailed or twotailed. Calc mean if it's a cont variable. then calc std error. Then plug into formula and take absolute value of answer  that's the zscore. look up zscore on table and find pvalue. if it's a twotailed hypothesis, multiply pvalue by 2. If p<.05, reject the null with 95% certainty If p<.01, reject the null with 99% certainty 


Term

Definition
1. Subtract the second variable from the first variable, create a column of differences 2. Calculate the mean of the column of differences 3. Calculate the standard error of the column of differences 4. Calculate degrees of freedom = (number of nonmissing observations – 1 ) 5. Calculate T = ( mean / standard error ) 6. Use the Tscore table. Find the row that matches up to the degrees of freedom. Look up on table. If your Tvalue is BIGGER than the value for t.025, for example, the means are significantly different at the .025 level for a onetailed test, and .05 for a two tailed test. If smaller, there's minimal difference between the two means 


Term
steps for chisquare test and when to use it 

Definition
use it to test the amt of correlation between two categorical variables create cross tab. add 'total' column and row. calc expected freqs, plug into chisquare formula for each cell, add up those  that's the chisquare value. calc degrees of freedom and look up in table.
If your chisquare value is BIGGER than the value for .025, the association is significant at the .025 level 


Term

Definition
order observations smallest to largest Divide the percentile N by 100, and multiply number of observations. If this number has a decimal, round up  Starting from the smallest value, count up as many observations as the number derived in step 3. The value in that observation is the Nth percentile ***if the number from step three is a whole number before rounding, count up from smallest observation that number and that number plus 1. Add the two and divide by 2 to get percentile 


Term

Definition
order observations smallest to largest multiply # of observations times 0.5 if decimal round up Starting from the smallest value, count up as many observations as the number derived in step 3. The value in that observation is the Nth percentile ***if the number from step three is a whole number before rounding, count up from smallest observation that number and that number plus 1. Add the two and divide by 2 to get percentile 


Term
std error for binary variables 

Definition
use 2nd formula under "Margin of Error" on formula sheet (one w/ "p" value) 


Term
how to calc margin of error 

Definition
count number who gave each answer (Y) and (N) compute the proportion who gave the first answer using this formula: p= ___Y_____ Y + N calc std error using the pvalue calc' in previous step plug into this formula: p + or  1.96 *SE for 95% confidence (replace 1.96 with 2.58 for 99% confidence) 


Term
N and m in Kendall's tauc 

Definition
N is the number of observations in the table (not the number of cells). add up all the numbers in the cells to get it.
m is the either the number or rows or columns – whichever is smaller. 


Term
How they fool you with stats 

Definition
Nonrandom samples, Improper generalization (Republicans won more seats in the last election, but that does not necessarily mean voters want more restrictive abortion law), Small samples / No standard deviations (margins of error) reported, Selfselected respondents, Loaded questions: 


Term
Convert odds ratio to percent 

Definition
subtract one and multiply by 100 

