Introduction to Biostatistics: Assignment 2 Solutions

Running head: INTRODUCTION TO BIOSTATISTICS 1
401077 Introduction to Biostatistics, Spring 2018
Assignment 2
Due Sunday September 23, 2018
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Your name: Mary Spandana Pudota
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INTRODUCTION TO BIOSTATISTICS 2
Question 1
a. Point estimate of proportion of females.
According to the data, females are 128 while males are 271. The point estimate of females is;
The point estimate for female p= 128
271 = ¿ 0.47
The 95% confident interval is;
Confidence Interval= p ± Z α
2
. √ p ( 1−p )
n
Confidence Interval=0.47 ± 1.96 √ 0.47 ×0.53
195
¿ 0.47 ± 1.96 ×0.044
Confidence Interval=¿ Or; 0.41<p<0.53
According to R data
Statistics-proportion-single sample proportion test-sex-ok
Point estimate for female is 0.47
95% Confidence interval ranges between 0.4136887- 0.5317344
b. The proportion of girls to boys is 0.47, therefore, the confidence interval tells us that
when we are 95% confidence with the data we have, then the lower limit of girl’s
proportion is 0.41 while the highest limit the proportion can go is 0.53. Hence the point
estimate is inclusive in the confidence interval.
c. The result in part (b). is consistent with the statement 50% of 17-year-old in NSW are
females since the confidence interval ranges between 0.41- 0.53.

INTRODUCTION TO BIOSTATISTICS 3
Question 2
a.
Fig 1. Histogram
Based on the histograms above, it is evident that the highest number of hours on both males and
females lies 0-3 hours with a frequency of 60 while that of least number of hours for females lies
20-25 and males lies within 17- 20 hours. The graphs show the distribution of the number of
hours for MVPA on each gender.
Sex Mean SD IQR Skewness 0% 25% 50% 75% 100% MVPA:n
Femal
e
3.857031 3.66875
9
3.90 2.292525 0.3 1.3 2.85 5.20 23.0 128
Male 4.546154 4.13621
5
5.45 1.152940 0.2 1.2 3.10 6.65 17.7 143