Week 8 data distribution

Question 1

What does a normal distribution look like

Answer 1

symmetrical and bell shaped with most scores focused towards the middle

Mean, mode and median are equal

Question 2

What mathematically defines a normal distribution

Answer 2

mean and standard deviation

Question 3

What is the range of skew

Answer 3

-infinity to +infinity

Question 4

What is the general rule for analyzing slowness

Answer 4

If the z-score of skewness (skewness/standard error of skewness) is > 1.96, the data is substantially skewed

Question 5

What determines direction of skew

Answer 5

direction of tail

Question 6

What does the order of central tendency look like on a negatively skewed graph

Answer 6

mean, median then mode is greatest

Eg on a test, most students score well but very few low (outliers) reducing the mean

Question 7

What does the order of central tendency look like on a positively skewed graph

Answer 7

mode, median then mean the greatest

Most data points concentrated to lower end.

Eg income levels where most people earn less but some outliers earn a lot more

Question 8

Kurtosis

Answer 8

altitude or peak of distribution

Question 9

What is the range of kurtosis

Answer 9

-2 (flat) to +infinity

Question 10

3 types of kurtosis

Answer 10

1. Mesokurtic
2. Platykurtic
3. Leptokurtic

Question 11

Mesokurtic

Answer 11

Neutral degree

Question 12

Platykurtic

Answer 12

flat but thick in shoulders

Wide peak

Question 13

Leptokurtic

Answer 13

peaked, thick in Centre and tails

Question 14

What is the normal curve called in kurtosis

Answer 14

Mesokurtic

Question 15

What is general rule for analyzing kurtosis

Answer 15

if the z score of kurtosis aka kurtosis/standard error of kurtosis is > 1.96, then the data is significantly different from Mesokurtic

Question 16

Unimodal

Answer 16

1 peak

Question 17

Bimodal

Answer 17

2 peaks

Question 18

Multimodel

Answer 18

more than 2 peaks

Question 19

What could be a cause of bimodal distributions

Answer 19

Ptsp may be not good at study so eg take longer first try but shorter second producing vastly different scores

Question 20

in non-linear transformations…

Answer 20

all values for a particular variable are transformed

Question 21

how to non-linear transform positively moderate skewed data

Answer 21

take the square root of each value

Question 22

how to non-linear transform positively more substantial skewed data

Answer 22

take the logarithm of each value

Question 23

how to non-linear transform positively severe skewed data

Answer 23

take the reciprocal transformation for each value

Question 24

what do you do first when you want to non-linear transform negatively skewed data

Answer 24

first reflect the score, x-1 to have a positive skew

Question 25

how to non-linear transform negatively moderate skewed data

Answer 25

take the square root of each value

Question 26

how to non-linear transform negatively substantial skewed data

Answer 26

take the logarithm

Question 27

how to non-linear transform negatively severe skewed data

Answer 27

take the reciprocal

Question 28

why do we transform data

Answer 28

bring it to a normal shape

change the measure

correcting skew for stats test

Question 29

difference between non linear and linear transformations

Answer 29

non linear change the shape of distribution scores

linear DONT change the shape of the distribution or have an effect on stats analyses - allows us to express data in different units

Question 30

how can you linear transform data

Answer 30

multiply or divide by a constant

add or subtract a constant

combination of both

Question 31

what is the mean and SD of a normal distribution

Answer 31

mean = 0

SD = 1

Question 32

what does the value of z tell us

Answer 32

how many standard deviation units a particular score is from the mean

Question 33

what does a positive z score indicate

Answer 33

observation is greater than the mean

Question 34

what does z score magnitude or absolute value tell you

Answer 34

how far a score or observation is from the mean

Question 35

what does z-score allow us to calculate

Answer 35

the probability of obtaining a particular score within the distribution/area under the curve