Download MEAN

Evaluating Data in Research
Joey finished at the 74th percentile on his
EOC Algebra test.

74th percentile means
Above 74% of test takers
 Actual #75, there is no 100th percentile

 We
look for……..




A measure of central tendency is a single score
that represents a whole set of scores.
Mean –
 Average
 most easily skewed by outliers (extreme
numbers)
Median
 Middle value (midpoint, or 50th percentile)
 (Place in sequential order and find middle
number)
Mode
 Most frequently occurring score

A Skewed Distribution
90
15 20 25 30 35 40 45 50
475
70
Mode Median
One Family
Mean
Income per family in thousands of dollars
710
Measures of variability
RANGE: difference between the highest and
lowest scores (can be deceptive due to outliers)
MEAN
7
6
1
11
5
4
3
2
1
1
2
3
4
5
6
7
8
9
10
11
12
measures of variability
STANDARD DEVIATION: how much any
given score differs from the average, or mean
score
+1 sd
-1 sd
MEAN
7
6
5
4
3
2
1
1
2
3
4
5
6
7
8
9
10
11
12
The more spread out the scores, the larger the
STANDARD DEVIATION.
+1 sd
MEAN
-1 sd
7
6
5
4
3
2
1
1
2
3
4
5
6
7
8
9
10
11
12



1 SD = 68% of scores
2 SD = 95% of scores
3 SD = 99.7% of scores

2 High School punters
Kicker A:
 mean distance: 39.8 yds
 Standard deviation: + 14 yds.
 Kicker B:
 mean distance: 34.5 yds.
 Standard deviation: + 4 yds.


Which player do you play?
• Player B – team will know where to run

Z score




number that represents how many SD’s a particular
score differs from the mean
The mean score for the class was 80, with a SD
of 10.
Joey scored 60 on his test. What’s his z score?
Betsy scored a 95. what is her z score?
When is a study’s data significant?
 When there is a significant difference between
the results (data) for the control group and
experimental group.
 When the data is reliable (consistent)

1. What is the mean of the following
distribution of scores: 2, 3, 7, 6, 1, 4, 9, 5, 8, 2?
A. 5
B. 4
C. 4.7
D. 3.7
E. 6
Answer: c
2.
What is the median of the following
distribution of scores: 1, 3, 7, 7, 2, 8, 4?
a. 1
b. 2
c. 3
d. 4
Answer: d
3.
What is the mode of the following
distribution: 8, 2, 1, 1, 3, 7, 6, 2, 0, 2?
a. 1
b. 2
c. 3
d. 7
Answer: b
4.
Seven members of a Girl Scout troop report the
following individual earnings from their sale of
candy: $4, $1, $7, $6, $8, $2, and $7. In this distribution
of individual earnings:
a.
b.
c.
d.
e.
The mean is equal to the mode and equal to the median
The mean is less than the mode and equal to the median
The mean is equal to the mode and greater than the median
The mean is greater than the mode and greater than the
median
The mean is less than the mode and less than the median
Mean=5, median=6, mode=7
Answer=e
Ethics in Research
APA Ethical Guidelines
– Informed Consent
– No harm to patients
– Confidentiality
– Debriefing
Animal Testing

Statistics to consider…
30,000,000 animals used for research each year
constitutes 1% of animals killed each year to
eat.
 200,000 dogs and cats researched annually /
animal shelters euthanize 50x that each year

Is it morally acceptable to place the wellbeing of humans above other animals
regarding research?