# paired t test

Wikipedia says:

“….

Paired samples t-tests typically consist of a sample of matched pairs of similar units, or one group of units that has been tested twice (a “repeated measures” t-test).

A typical example of the repeated measures t-test would be where subjects are tested prior to a treatment, say for high blood pressure, and the same subjects are tested again after treatment with a blood-pressure lowering medication. By comparing the same patient’s numbers before and after treatment, we are effectively using each patient as their own control.

…”

http://en.wikipedia.org/wiki/Student%27s_t-test#Paired_samples

http://www.stats.gla.ac.uk/glossary/?q=node/355

http://www.gla.ac.uk/sums/users/jdbmcdonald/PrePost_TTest/pairedt1.html

# One sample t test

The one sample t test is used to test sample data against the Null Hypothesis (H0). In this case the Null Hypothesis is whether the sample mean matches the population mean.

# chi square test statistic

The Chi square compares the observed data with the Null Hypothesis.

Chi square test looks at single set of data and Null Hypothesis.

• Ho The no difference or no association hypothesis that shows no difference between observed and expected data.
• H1 This postulates that there is a difference between observed and experimental data.

Expected = row X col total / grand total

χ2 = sum ((observed – expected) /Expected)2

χ2  and DF/degree of freedom gives the test statistic

A big difference between observed and expected results in a large test statistic (χ2) and so leads to a rejection of the Null Hypothesis (Ho)

The greater the value of the test statistic, the greater the evidence against the Null hypothesis -leads to a smaller p -value

“…The p-value is the area under the chi-square probability density function (pdf) curve to the right of the specified χ2 value…” http://www.di-mgt.com.au/chisquare-calculator.h

Source: di mgt.com.au

p value is the area to the right of the test statistic. The less the number (< 0.05) the more likely to reject the Null Hypothesis

http://www.stat.ucla.edu/~kcli/stat13/stat13-lecture14.pdf

Nice video explaining it all.

# Cat Now Found in Hollingdean and Hollingbury

Missing. Found!

A neighbour at the end of the road spotted one of our notices and she’s back home. Skinny but looks OK.