Statistical tests - A-level Flashcards
when is Mann Whitney U used
-unrelated data (independent groups)
- ordinal data
-test of difference
how is the data used in Mann Whitney U
in a table of ranks
what is a table of ranks in Mann Whitney U
lowest is given a rank of 1. if multiple data points are the same value the positions they would be are added and mean is calculated
how can ranks in Mann Whitney U be shown
frequency table
what is the value of u in Mann Whitney U
calculated and is the smaller of the values
how is Mann Whitney U seen as being significant
if the value of u is less than the critical value so the null hypothesis can be rejected and alternative hypothesis accepted
when is Wilcoxon used
-looking for a difference
-related design (repeated measures)
-ordinal data
how is ranking used in Wilcoxon
-done between difference in the two sets of data (signs are ignored during ranking)
-if the difference is 0 the data is not included in the ranking and is deducted from the N value
what is the T value in Wilcoxon
calculated value
how is the T value calculated in Wilcoxon
sum of the less frequent sign
how is Wilcoxon seen as significant
is the calculated value of T is less than the critical value the null hypothesis can be rejected and the alternative hypothesis accepted
is Mann Whitney U and Wilcoxon parametric tests
No, they are non-parametric tests
when is an unrelated t-test used
-looking for a difference
-interval data
-unrelated data (independent groups)
-criteria for parametric test must also be filled
what is the criteria for a parametric test
-level of measurement is interval
-normal distribution
-homogeneity of variance (as standard deviations of both groups are similar)
table of data in an unrelated t-test
-calculate sum of scores for A
-repeat for B
-square each value in the A group and calculate the sum of the squared values
-repeat for group B
what is the calculated value in an unrelated t-test
t value
when is an unrelated t-test significant
if the calculated value of t is greater than the critical value the difference is significant and the null hypothesis can be rejected and alternative hypothesis can be accepted
are the related t-test and unrelated t-test parametric tests
yes
criteria for a related t-test
-looking for a difference
-related design (repeated measures)
-interval data
-requirements for a parametric test must also be met
how is the data table used for related t-test
-calculate the difference between scores for condition A and B
-add the sum of the differences
-square each difference
-add the sum of the squared differences
what is the calculated value called in a related t-test
t value
when is results from a related t-test significant
when calculated value of t is greater than the critical value the difference is significant so the null hypothesis can be rejected and the alternative hypothesis accepted
are pearsons and spearman’s tests of correlation
yes
what is the criteria for spearman’s rho
-looking for a correlation
-ordinal data in one or bother is the variables) can be used with interval data)
what direction of correlation is wanted with spearman’s rho
positive correlation
how are the ranks decided on spearman’s rho
form lowest to highest. if two cores share the same ranks, the mean of their total ranks is calculated
how is the difference calculated in spearman’s rho
-find the difference between each pair of ranks
-square the differences
-add the squared differences
what is the calculated value called in spearman’s rho
rho
when is difference significant in spearman’s rho
when the calculated value of rho is greater than the critical value the difference is significant and the null hypothesis is rejected and the alternative hypothesis accepted
conditions for pearson’s r
-looking for correlation
-interval data
-must also meet criteria for a parametric tests
how is the table of data used for pearson’s r
-there are scores of x and y
-the sum of scores for the x and sum of scores for the y must be calculated
-square each x and y value
-calculate sum of x squared and then sum of y squared
-multiply x and y for each participants and then add these values together
what is the calculated value in pearson’s r called
r
when are results for pearson’s r significant
when calculated value of r is greater than the critical value difference is significant and null hypothesis can be rejected and alternative hypothesis can be accepted
conditions for chi-squared
-can be used for test of difference or association
-unrelated design (independent groups)
-nominal data
what is the contingency table in chi-squared
shows observed frequencies and totals for each row, column and overall total are calculated
what is table of expected frequencies in chi-squared
calculated for each cell by multiplying the total for the row by the total for the column divided by the grand total
what is the calculated value for chi-squared
X^2
when is chi-squared significant
when the calculated value is greater than the critical value difference is significant so the null hypothesis can be rejected and alternative hypothesis accepted
how are degrees of freedom calculated for chi-squared
(rows-1) x (columns-1)
how are degrees of freedom for unrelated t-test calculated
total sample size -2 (Na+Nb-2)
how are degrees of freedom for related t-test calculated
sample size-1 (N-1)
how are degrees of freedom calculated for pearson’s r
sample size -2 (N-2)
what are descriptive statistics
include measures of central tendency such as the mean, mode and median as they provide an average figure from the data set. also includes measures of dispersion such as standard deviation and range as these show the spread of data
what are inferential statistics
discover if the the results are statistically significant, as this means they are unlikely to have occurred through chance
