# MATH 6627 2010-11 Practicum in Statistical Consulting/Students/Andy Li

## Contents

#### Welcome to my wiki page for the Statistical Consulting Practicum

My name is Andy Li. From 2008, I started undergraduate in Statistics in York. After two years study, I am now a master student in Applied Statistics. I have another bachelor degree in Chemical Engineering. I have worked as a B2B salesman for many years. I used SAS, R, matlab, minitab and Maple in the classes. I am very happy to join our 6627 team to know more about Statistics. Hope we can build up not only our knowledge but also our friendship in these following days.

## Sample Exam Questions

### Week 1

(In class) There are 11 students in the 6627 class, 5 of which are male. There is a statistics meeting in the campus. All the student want to attend as visitors, but the problem is there are only 6 seats left. So, professor needs to choose 6 students randomly and wants two of them to be male, to help setting up the tables. How many ways can he select students for his experiment?

### Week 2

(In class)We have the cloud of our data, data ellipse and the centre point. We also know about 40% data falling into the inside ellipse and 86% data in the outside ellipse. What is the radius of the outside ellipse? What is Sx,Sy,Sy.x and 95% confidence interval?

### Week 3

Q: Explain the multiple regression Coefficients in three dimensions.

A: Beta0 defines the Y-intercept of the plane. Beta1 defines the slope of the plane along the x1 axis, and beta2 defines the slope of the plane along the x2 axis. The error term ε adds noise to the plane so that it is bumpy instead of being perfectly smooth.

### Week 4

Q: Which is talking about correlation and what is about interaction? a) people with more years in jail tend to have fewer years of education. b) The more money I save, the more financially secure I feel. c) To give a good taste, she squeezed a lemon into her black tea and stired the tea. d) Helping others in Stats lab is one of our TA job. Another type is grador e) Steel has the ability to become harder and stronger through adding carbon to it and quenching (rapidly cooling). f) The more years of education I complete, the higher my earning potential. g) Proffessors drink too many coffee, because their work is stressful.

## Statistics in the Media

### Week 1

Can you see 2010 is crisis year? It's NOT the time to change! 18 Scary US Debt Facts

If there is no statistics, the people over the border may toast to celebrate the big success of this year this time.

### Week 2

4-day conference begins at BHU Banaras Hindu University (BHU), Hindi: काशी हिन्दू विश्वविद्यालय, is a premier central university and a world class educational institution located in Varanasi, India. It is regarded as the largest residential university in Asia.

### Week 3

This is a current news with a very old topic. This is provided by two of Canada's leading think tanks: Sustainable Prosperity and Pembina Institute, talking about a well known common sense. This is "Putting Transportation on Track" , with nothing new.

### Week 4

In Jan. 18, 2011, 2010 US Census data is accessable online. It is easy to reach and will be appreciated by many fact finders. The other thing in the high light is the suvery itself. It only asks just 10 questions and takes about 10 minutes to complete.

## Questions and Comments on Groupwork and Class Lectures

### Week 1

For the example about smoking and life expectation we discussed in class, I think there are two more factors we should take into consideration. One is the smoke starting age. I know kids smoke in some poor countries, because they don't know it is harmful. Another is the different type of cigarette has different effect. Although whatever the type of cigarette that you smoke, it will always be ‘injurious to health’. But the cigarettes in rich countries have relatively less addictive nicotine and tar, also are equipped with long filters and not allowed to add harmful favor additives. I know this because I was a heavy smoker before, and had smoked more than 100 brands of cigars, which come from different countries. But yes, I am still alive.

### Week 2

Some classmates couldn't install the package of spida and p3d. Below is the procedure you should follow:

3. do a short installation of R.

4. run

> install.packages( c("car","rgl"))

> install.packages( c("spida","p3d"), repos = "http://R-Forge.R-project.org")

### Week 3

It's really amazing to see the data moving by using GoogleVis and p3d in last lecture. It will be very useful in consulting or presentation. I think there is limitation to use these methods to analyze complex models. But we may choose 3 variables each time from a multiple model to draw a 3d plot to see the trend.

### Week 4

Carrie has a question about the sign: In the slides for Visualizing Multiple Regression in the section on data ellipse for predictors (page 30), but the general predictor has a notation I'm not familiar with and missed in lecture. What does the plus sign in a in a circle mean?

Answer: The plus sign in logical operation is called "exclusive or". Wiki link is here. But in the notes, it is specially defined in summary, Page 88.