Question

You are a botanist looking at variation in flower morphology along the central coast and of special interest to you is a species of native sunflower. You think that there's a difference in the number of petals between some populations: population1 and population 2. You believe that population 2 has more petals. You count the number of petals in both populations and get the data.

a.) write a properly worded hypothesis and prediction for this study.

b.) Do the populations have different numbers of petals? Use Rstudio to perform an appropriate statistical test and write a properly formatted results statement.

Data:

Population	Petals
Pop 1	1
Pop 1	29
Pop 1	23
Pop 1	30
Pop 1	26
Pop 1	26
Pop 1	5
Pop 1	14
Pop 1	11
Pop 1	3
Pop 1	8
Pop 1	15
Pop 1	14
Pop 1	22
Pop 1	28
Pop 2	39
Pop 2	11
Pop 2	10
Pop 2	30
Pop 2	26
Pop 2	31
Pop 2	19
Pop 2	15
Pop 2	22
Pop 2	33
Pop 2	32
Pop 2	16
Pop 2	32
Pop 2	33
Pop 2	19

Answer 1

a)

Null and Alternate Hypothesis

H₀: µ₂ = µ₁(Mean Petals count of Population 2 is same as that of Population 1)

H_a: µ₂ > µ₁ (Mean Petals count of Population 2 is greater than that of Population 1)

b)

Code:

# Read Data

setwd ("D:/Data")

mydata <- read.csv("Data_23Nov19.csv", header = T)

head(mydata)

pop1 = mydata[mydata$Population=="Pop 1",]

pop2 = mydata[mydata$Population=="Pop 2",]

t.test(pop2$Petals,pop1$Petals, paired = FALSE,alternative = "greater")

Output

        Welch Two Sample t-test

data:  pop2$Petals and pop1$Petals

t = 2.1594, df = 27.778, p-value = 0.0198

alternative hypothesis: true difference in means is greater than 0

95 percent confidence interval:

 1.59719     Inf

sample estimates:

mean of x mean of y 

 24.53333  17.00000 

Result

Since the p-value is less than 0.05, we reject the null hypothesis in favour of alternate hypothesis.

Conclusion

Mean Petals count of Population 2 is greater than that of Population 1