moss.cover.analysis.txt
				JM 10/23/2026

# ESCI 197C  Intro to Field Research
# Moss distribution project, 10/2/2026

##########################################################################
# This section contains R commands only; see below for R output
# This example uses fabricated data. You should use your own field measurements
# Example: moss %cover on upward vs. downward sloping surfaces of Bigleaf maple trunks
# Use Two sample t-test to compare means.
# Often % data are transformed to normality using arcsine transformation. (not done below)

# Enter data
moss.up <- c(74, 50, 80, 68, 75, 48, 90, 95, 100, 40)
moss.up

moss.down <- c(60, 50, 40, 35, 45, 50, 75, 30, 65, 60)
moss.down

# sample means:
mean(moss.up)
sd(moss.up)
mean(moss.down)
sd(moss.down)

# Compare average moss cover among samples, using t-test function in R:
t.test(moss.up, moss.down, alt="two.sided")

# Conclude large difference in averages (21%), with high confidence (p<0.02)

##########################################################
> # This section contains R commands and R output
> # This example uses fabricated data. You should use your own field measurements
> # Example: moss %cover on upward vs. downward sloping surfaces of Bigleaf maple trunks
> # Use Two sample t-test to compare means.
> # Often % data are transformed to normality using arcsine transformation. (not done below)

> # This example uses fabricated data. You should use your own field measurements
> # Example: moss %cover on upward vs. downward sloping surfaces of Bigleaf maple trunks
> # Enter data
> moss.up <- c(74, 50, 80, 68, 75, 48, 90, 95, 100, 40)
> moss.up
 [1]  74  50  80  68  75  48  90  95 100  40
> 
> moss.down <- c(60, 50, 40, 35, 45, 50, 75, 30, 65, 60)
> moss.down
 [1] 60 50 40 35 45 50 75 30 65 60
> # sample means:
> mean(moss.up)
[1] 72
> mean(moss.down)
[1] 51
> 
> # sample means:
> mean(moss.up)
[1] 72
> sd(moss.up)
[1] 20.58586
> mean(moss.down)
[1] 51
> sd(moss.down)
[1] 14.1028
> 
> # Compare average moss cover among samples, using t-test function in R:
> t.test(moss.up, moss.down, alt="two.sided")

        Welch Two Sample t-test

data:  moss.up and moss.down
t = 2.6613, df = 15.923, p-value = 0.01712
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
  4.265409 37.734591
sample estimates:
mean of x mean of y 
       72        51 

> # Conclude large difference in averages (21%), with high confidence (p<0.02)