I am Jayson L. I am an R Homework Expert at statisticsassignmenthelp.com. I hold a Master's in Statistics, from The University of Sheffield, UK. I have been helping students with their homework for the past 6 years. I solve assignments related to R. Visit statisticsassignmenthelp.com or email info@statisticsassignmenthelp.com. You can also call on +1 678 648 4277 for any assistance with R Homework.

1. For any Homework related queries, Call us at : - +1 678 648 4277
You can mail us at : - support@statisticsassignmenthelp.com or
reach us at : - https://www.statisticsassignmenthelp.com/

2. The following solution for data analysis using r shows how r is used to find the t-test and
other parameters based on two different types of data. It also involves testing hypotheses,
making decisions, and explaining the reason behind every decision.
Data
Before Therapy after Therapy
11 12 32 23
12 9 16 30
15 13 18 19
7 6 26 27
10 11 18 30
8 7 11 35
14 12 17 21
13 9 21 31
13 12 11 30
10 10 14 28
13 14 22 32
10 8 20 26
8 9 13 29
12 14 24 34
8 11 12
10 12 17
For this assignment, you are required to use the statistical program R. Round all numerical
answers to two decimal places and p values to three. The assignment is comprised of two
problems. Each problem requires you to calculate the appropriate t-test with R.
statisticsassignmenthelp.com
Problems and Solutions

3. A commonly held belief is that it is always beneficial to one's emotional health to vent
one's feelings after a traumatic event. A study attempted to actually test this idea.
Researchers tested the Emotional Well Being scores of subjects who had experienced a
traumatic event, before and after they received psychotherapy. Perform an appropriate
t-test with R to see if there is a difference in the Emotional Well Being scores before and
after the psychotherapy.
Finding the t-test and deciding on the hypotheses
Here, the means, standard deviations, and t-tests for the two different sets of data are
calculated. Conclusions on hypotheses on each are given, and the results are all
explained. The pooled variance is also calculated.
Finding the mean and standard deviation for the first set of participants
1a) what is the Mean for the Before Therapy group?
Answer: 10.875
1b)) what is the Standard Deviation for the Before Therapy group?
Answer: 2.390955
statisticsassignmenthelp.com

4. 1c) what is the Mean for the After Therapy group?
Answer: 10.5625
1d) what is the Standard Deviation for the After Therapy group?
Answer: 2.393568
Deciding on the appropriate test
1e) what type of t-test is required here?
Answer: paired sample t test
Deciding on the hypothesis
1f) based on your findings; can we reject the null hypothesis? Report your findings using
the format below, as demonstrated in lab. Be sure to clearly state the variables. If there is a
significant difference, clarify which direction it is going.
Answer: We cannot reject the null hypothesis. There is not a significant difference in mean
between before therapy and after therapy.
t(15)= 0.628 , p= 0.540
statisticsassignmenthelp.com

5. Problem 2
Researchers were interested in which of two methods were best for retention. They had
all subjects read a chapter in a textbook. Then, one group of subjects ('Study') was
encouraged to study the material for 60 minutes. The other group of subjects (‘Quiz’)
was not allowed to study, but was actually given a 60 minute quiz on the material. Then,
all subjects were required to complete a final test on the material. Perform an
appropriate t-test on the final test scores with R to see if there is a difference in
performance between the Study and Quiz groups
Finding the mean and standard deviation for the second set of participants
statisticsassignmenthelp.com

6. 2a) what is the Mean for the Study group?
Answer: 18.7857
2b) What is the Standard Deviation for the Study group?
Answer: 5.950806
2c) What is the Mean for the Quiz group?
Answer: 26.5
2d) what is the Standard Deviation for the Quiz group?
Answer: 6.449806
Deciding on the appropriate test
2e) what type of t-test is required here?
Answer: Independent two sample t test
statisticsassignmenthelp.com

7. Deciding on the hypothesis
2f) based on your findings; can we reject the null hypothesis? Report your findings using
the format below. Be sure to clearly state the variables. If there is a significant difference,
clarify which direction it is going.
Answer:
We can reject the null hypothesis. There is a significant difference in the mean between
before and after.
T ( 28) = -3.3873, p= 0.002
Finding the Pooled Variance
2g) Calculate the Pooled Variance (𝑠𝑝
2) for this same t-test by hand. Hint: To save much
time, use the Standard Deviations from the R output. Round to two decimals places. You
do not have to show your calculations.
Pooled Variance (𝑠𝑝
2) = 6.22
Q3
###############
statisticsassignmenthelp.com

8. > #Q1
> Assign3 <- read.delim("C:/Users/CSSC/Downloads/Assign3.tx
t")
> ETURN<-data.frame(Assign3)
> mean(ETURN$BeforeTherapy,na.rm=TRUE )
[1] 10.875
> sd(ETURN$BeforeTherapy, na.rm = TRUE)
[1] 2.390955
> mean(ETURN$AfterTherapy, na.rm= TRUE)
[1] 10.5625
> sd(ETURN$AfterTherapy)
[1] 2.393568
> t.test(ETURN$BeforeTherapy,ETURN$AfterTherapy,paired = TR
UE, na.rm= TRUE)
Paired t-test
statisticsassignmenthelp.com

9. data: ETURN$BeforeTherapy and ETURN$AfterTherapy
t = 0.62795, df = 15, p-value = 0.5395
alternative hypothesis: true difference in means is not equ
al to 0
95 percent confidence interval:
-0.7482174 1.3732174
sample estimates:
mean of the differences
0.3125
> #Q2
> mean(ETURN$Study,na.rm= TRUE)
[1] 18.78571
> sd(ETURN$Study, na.rm=TRUE)
[1] 5.950806
> mean(ETURN$Quiz, na.rm=TRUE)
[1] 26.5
> sd(ETURN$Quiz, na.rm=TRUE)
[1] 6.449806
> t.test(ETURN$Study,ETURN$Quiz, na.rm=TRUE)
Welch Two Sample t-test
statisticsassignmenthelp.com