Question

STAT101
PatientID	Age	Sex	County	CardioRisk	Height	Weight	BloodGroup	Stroke	RegularEx	Group	Cholesterol1	Cholesterol2
225	58	Male	Offaly	Low	178.2	103.5	AB	N	N	Placebo	6.1	4.6
226	61	Male	Carlow	Medium	173.9	63	AB	Y	N	Control	2.2	5.7
227	57	Female	Donegal	Medium	160.9	76.1	B	N	Y	Control	5.8	5
228	43	Male	Offaly	High	175	83.7	AB	Y	N	Control	3.6	2.4
229	37	Female	Longford	Low	156.8	68	B	N	Y	Control	4.9	6
230	29	Male	Leitrim	Medium	165.1	79.1	A	Y	Y	Placebo	3.5	5.3
231	52	Male	Cavan	Low	166.6	60.4	A	Y	Y	Placebo	2.9	4
232	47	Female	Westmeath	Low	166.8	63.6	B	N	Y	Control	4	3.2
233	28	Male	Wicklow	Low	171.5	67.2	O	Y	N	Control	4.2	4

Q1

The commands for these questions using rstudio

a. How many patients are in each of the Control and Placebo groups?

b. Provide a histogram and describe the distribution of age groups in your data.

c. Body Mass Index (BMI) is defined as kg/m2 where kg is the individual’s weight in kilograms and m

is the individual’s height in metres. Provide a histogram and describe the distribution of BMI in the

whole sample. Calculate the sample mean BMI of both males and females.

d. Identify the counties with the highest and lowest mean weights.

e. Compute how many females in the sample belong to Blood Group O.

f. What percentage of men belong to Blood Group B?

g. Calculate the mean difference in each subject’s cholesterol level from the start to the end of the study.

(Hint: create a new variable choldiff.)

Answer 1

R codes and output:

> d=read.table('data1.csv',header=T,sep=',')
> head(d)
PatientID Age Sex County CardioRisk Height Weight BloodGroup Stroke
1 225 58 Male Offaly Low 178.2 103.5 AB N
2 226 61 Male Carlow Medium 173.9 63.0 AB Y
3 227 57 Female Donegal Medium 160.9 76.1 B N
4 228 43 Male Offaly High 175.0 83.7 AB Y
5 229 37 Female Longford Low 156.8 68.0 B N
6 230 29 Male Leitrim Medium 165.1 79.1 A Y
RegularEx Group Cholesterol1 Cholesterol2
1 N Placebo 6.1 4.6
2 N Control 2.2 5.7
3 Y Control 5.8 5.0
4 N Control 3.6 2.4
5 Y Control 4.9 6.0
6 Y Placebo 3.5 5.3
> attach(d)
The following objects are masked from d (pos = 3):

Age, BloodGroup, CardioRisk, Cholesterol1, Cholesterol2, County,
Group, Height, PatientID, RegularEx, Sex, Stroke, Weight

Que.a

> length(which(Group=='Placebo'))
[1] 3
> length(which(Group=='Control'))
[1] 6

3 patients in placebo group and 6 patients in control group.

Que.b

> hist(Age)

Que.c

> BMI = round(Weight/(Height)^2,4)
> hist(BMI)
> a=cbind(Sex, BMI)
> a
Sex BMI   
[1,] "Male" "0.0033"
[2,] "Male" "0.0021"
[3,] "Female" "0.0029"
[4,] "Male" "0.0027"
[5,] "Female" "0.0028"
[6,] "Male" "0.0029"
[7,] "Male" "0.0022"
[8,] "Female" "0.0023"
[9,] "Male" "0.0023"
> bmi_m = BMI[which(Sex=='Male')];bmi_m
[1] 0.0033 0.0021 0.0027 0.0029 0.0022 0.0023
> bmi_f = BMI[which(Sex=='Female')];bmi_f
[1] 0.0029 0.0028 0.0023
> mean(bmi_m)
[1] 0.002583333
> mean(bmi_f)
[1] 0.002666667

Histogram:

Sample mean BMI for male =  0.00258

Sample mean BMI for female = 0.00267

Que.e

> length(which(Sex=='Female' & BloodGroup == 'O' ))
[1] 0

There are zero females in the sample belong to Blood Group O.

Que.f

> length(which(Sex=='Male' & BloodGroup == 'B' ))
[1] 0

There are zero males in the sample belong to Blood Group B. Hence percentage is zero.

Que.g

> choldiff= Cholesterol2 - Cholesterol1
> mean(choldiff)
[1] 0.3333333

The mean difference in each subject’s cholesterol level from the start to the end of the study is 0.3333