PSY230:
Introduction
– What can I expect in this course?
Trudy Kuo, Ph.D.
Misconception about statistics #1

There is a lot of math in this statistics course.
◦ Some formulas are used to help with the understanding of the
concepts.
◦ In reality, software programs actually do the calculations for
researchers.
◦ The application of the concepts is the most critical aspect of
learning statistics.
Misconceptions about statistics #2

I’m here only because I have to. I won’t be doing research
so I don’t need statistics.
◦ Statistics is in our daily lives, like it or not
◦ Statistical knowledge empower your thinking about everyday
stuff
“Poll: Clinton Opens Up Double-Digit Lead Over Trump”
NBC News headline on Aug. 9, 2016
http://www.nbcnews.com/politics/2016-election/poll-clinton-opens-double-digit-lead-over-trump-n6256
Then we realize how much we don’t know about the numbers…
How did they get the two percentages to plot for the two
candidates exactly?
• How many people did they ask?
• Who were those people?
• How much error margin is there with the percentage score? Is it
big enough to make the Clinton-Trump difference meaningless?
• Looking at the longer time line, would this difference be random
fluctuations over time?
Statistical reports often have more to do with the intended
purpose of report than anything else.
“Does fasting on alternate days work? A new study weighs in”
CNN Health News on May 1, 2017
http://www.cnn.com/2017/05/01/health/fasting-weight-loss-obesity-study/index.html
Main result:
“By the end of the yearlong diet sessions, those in the alternate-day fasting
group lost about 6% of their original body weight, whereas those in the calorie
restriction group lost 5.3%, Varady said.”
Questions to ask:
 Is this difference between 6% and 5.3% significant and meaningful?
 How many participants? Do they have similar health profiles?
 Did they really monitor subjects for a whole year?
Significance and effect size:
“… both the alternate-day fasting and calorie restriction groups experienced similar
weight loss amounts on average”
 It appears that the difference between 6% and 5.3% was not statistically significant.

Sample size consideration:


“The study involved 100 obese adults in Chicago and was conducted between 2011 and 2015.
The adults were randomly assigned to three groups. For one year, each group had to adhere to
an alternate-day fasting diet, a calorie-restriction diet or no diet.”
“The dropout rate in the alternate-day fasting group was 38%, versus 29% in the daily calorierestriction group, the researchers found.”
Study procedure consideration:

Members in the fasting and calorie counting groups were provided meals for the first three
months of the study and then were on their own for the last nine months… all participants were
provided with counseling on portion sizes and how to monitor calories and read food labels, she
said.
A word about my lectures
Goal #1:
 To explain critical concepts in a way that is different from the textbook.
Goal #2:
 To provide step-by-step instruction on how to work through a problem
(mostly Excel, a little SPSS later)

My terminology and symbols may be slightly different from that in the
textbook because the textbook tries to use more “user-friendly” terms that
are not always used by other researchers or statisticians.You may use any
term or symbol from either source as long as you demonstrate an
understanding of the concept.