BIOL 2060 - Fall 2021

Assignment 2

Due to Turnitin Thursday Nov. 11, 6:00 p.m.

In this assignment, you will use R Studio to

import a dataset from Excel that includes one categorical variable with 4 categories.

carry out a Chi-square goodness of fit test on the dataset.

make a grouped bar graph of the data.

Gastric and duodenal ulcers - painful sores in the lining of the upper digestive tract that can lead to internal bleeding or perforation of the tract - were shown, in the late 1980s, to be associated with infection by the bacteriumHelicobacter pylori.This discovery prompted renewed interest in anecdotal observations made nearly 40 years earlier that ulcer susceptibility is influenced by a patient's ABO blood type (= a scientific hypothesis).

On eClass you will find

1) an Excel file containing the ABO blood types of 181 randomly-selected ulcer patients (Rh blood type is not considered).

2) a recorded tutorial demonstrating the new R commands you will need - along with some of those you have already learned - to complete this assignment.

Download the Excel file and covert it (using "save as") to .csv format. Import the .csv file into R Studio and conduct a Chi-square goodness of fit test to compare the frequencies of ABO blood types in this group of patients with ABO frequencies in the general population. For the latter, see Table 5.5-1 in your text (also shown on slide 21 of lecture 6). Once you have completed the analysis, make a grouped (paired) bar graph to compare blood type frequencies in ulcer patients with those in the general population.

Different versions of the Excel data file are available to different students. You must use the file that is visible to you when you log in to your own eClass account.

Your report, to be submitted to Turnitin, should be in .doc, .docx or .pdf format (with embedded fonts) and should include the following:

A cover page indicating the assignment, the course, the date of submission, your name and student number (1 mark)

A second page with the following:

A statement of the null and alternate hypotheses (H0andHA) for your statistical test.

(2 marks)

R output showing the results of the Chi Square test (appearing under the heading

"Chi-squared test for given probabilities" in the console window) (2 marks)

A single-sentence conclusion with respect to the null hypothesis. (1 mark)

A single-sentence conclusion with respect to the scientific hypothesis (i.e., what can

be concluded about the relationship between blood type and susceptibility to

ulcers?) (2 marks)

A grouped bar graph copied and pasted from R studio. The graph should consist of 4

pairs of bars; each pair should show the frequency of an ABO blood type in ulcer patients and in the general population. Pairs should be arranged in decreasing order of frequency, with the most frequent blood typein the general populationshown on the left, and the least frequent on the right. A legend to indicate which bars correspond with which groups should be included. See the recorded tutorial for an example. (6 marks)

A third page with all the R code you wrote and used to carry out the assignment, copied and pasted from the source window in R studio. (6 marks)

Total mark is out of 20.

Y