Can I just say a big thank you to everyone on this forum for patiently contributing to my limited knowledge of statistics and holding up a light in the otherwise total darkness I experience with this subject.

This question relates to the weight of leaves on a sample of 90 trees measured prior cattle browsing, and the weight of leaves on a sample of 87 different trees taken post browsing.

Prior to browsing: 141.7 g of leaves <160 cm, 155.4 g of leaves >160 cm, (total leaves 297.1 g), sample size of 90

Post browsing: 34.9 g of leaves <160 cm, 169.6 g of leaves >160 cm, (total leaves 204.5 g), sample size of 87

So I followed the big R book on proportions, but the prop.test does not take into account sample size in the example in the book.

For example:

I multiplied by 10 to not have decimal places. Then I simple entered

Prop.test(c(prior to browsing <160cm, post browsing <160 cm), (total leaves prior to browsing, total leaves post browsing)

So this my result:

> prop.test(c(1417,349), c(2971,2045))

2-sample test for equality of proportions with continuity correction

data: c(1417, 349) out of c(2971, 2045)

X-squared = 496.77, df = 1, p-value < 2.2e-16

alternative hypothesis: two.sided

95 percent confidence interval:

0.2816133 0.3309540

sample estimates:

prop 1 prop 2

0.4769438 0.1706601

Is this appropriate? Would I be able to refer columns instead of values? Any advice on best practice appreciated!

Best wishes,

Lucy

Lucy

This question relates to the weight of leaves on a sample of 90 trees measured prior cattle browsing, and the weight of leaves on a sample of 87 different trees taken post browsing.

Prior to browsing: 141.7 g of leaves <160 cm, 155.4 g of leaves >160 cm, (total leaves 297.1 g), sample size of 90

Post browsing: 34.9 g of leaves <160 cm, 169.6 g of leaves >160 cm, (total leaves 204.5 g), sample size of 87

So I followed the big R book on proportions, but the prop.test does not take into account sample size in the example in the book.

**Does this matter? Can I include the sample size? Is this an appropriate approach?**For example:

I multiplied by 10 to not have decimal places. Then I simple entered

Prop.test(c(prior to browsing <160cm, post browsing <160 cm), (total leaves prior to browsing, total leaves post browsing)

So this my result:

> prop.test(c(1417,349), c(2971,2045))

2-sample test for equality of proportions with continuity correction

data: c(1417, 349) out of c(2971, 2045)

X-squared = 496.77, df = 1, p-value < 2.2e-16

alternative hypothesis: two.sided

95 percent confidence interval:

0.2816133 0.3309540

sample estimates:

prop 1 prop 2

0.4769438 0.1706601

Is this appropriate? Would I be able to refer columns instead of values? Any advice on best practice appreciated!

Best wishes,

Lucy

Lucy

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