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structure that can be manipulated. R has several forms of date structures but we will usesomething called POSIXlt. To convert from a string to POSIXlt we use the functionstrptime . Here is the code from lectures.

> dates dates dates reach reach wreach tab colnames(tab)

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"65+")

> rownames(tab) print(tab)

Try this for your data frames, use different rows (between 1 and 158).

Use barplot(tab, legend=TRUE, col=c("pink","lightblue")) to make a barplot.Investigate changing the colours ( col= ) and the beside= option.

2 Manual CalculationsThe purpose of this section is to give you practice of manual calculations for confidence intervals

for proportions and 2 tests. You shgould use your calculator to verify that you can get theseresults. If you don't have your calculator you can use R as a calculator .

2.1 Confidence Intervals for Proportions z 0. 025 = 1. 960 and z 0. 05 = 1. 645.

The proportion of males that reach a page is 89 out of 104 in a particular week. Finda 95% confidence interval for the proportion of males in the audience for this page.

ANSWER: (0.789, 0.923)

For 52 out of 200 find a 95% confidence interval for the proportion.

ANSWER: (0.199, 0.321)

For 441 out of 762 find a 90% confidence interval for the proportion.

ANSWER: (0.55, 0.608)

Your answers may be slightly different due to rounding.

Try this in R using prop.test (remember the results may be slightly different)

2.2 2 tests

Find the 2 statistic and the degrees of freedom for the following tables.

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