# SO5041: Lab Materials

## Week 12 Lab

## Hypothesis testing exam marks

Say that in last year's Leaving Cert English exam, the average mark achieved was 62.1%. A year
later, the Dept of Education wants quick feedback on whether the
standard has changed. A random sample of 100 scripts are assessed and
marked. Their average mark is 65.2% with a standard deviation of 12.4%

Conduct a test of the hypothesis that the standard has
changed, using a 95% level of confidence. Report and interpret
your findings.

## Independent Sample t-test in Stata

This file contains information on
gender and work hours for a UK sample (`use http://teaching.sociology.ul.ie/so5041/labs/week11a`

). Use summaries and graphs to
get a sense of the male-female differences, and then use an
independent sample t-test (i.e., `ttest `*varname*,
by(*groupvar*)

; replacing the variable names in italics
with the names of the appropriate variables).

## Correlation

This data file (`use http://teaching.sociology.ul.ie/so5041/labs/correl`

) contains six pairs of
variables, `X1`

and `Y1`

, `X2`

and
`Y2`

etc. First, graph all six pairs in scatterplots.
Also graph `X1`

with `Y2`

. What sort of
association do you see in each case (positive, negative, none,
strong, weak)? Make a guess what the value of the correlation
coefficient might be (write it down).

For each graph, get the correlation coefficient: e.g., `corr x1 y1`

. How do the reported correlation
coefficients correspond with those you guessed?

## Correlations with real data

With the data set ocorr.dta (`use http://teaching.sociology.ul.ie/so5041/ocorr`

), explore the
correlations between the variables it contains, graphically and with the
correlation coefficient.

Brendan Halpin

Dept of Sociology, University of Limerick

F2-025, x 3147; brendan.halpin@ul.ie