ch 3 descriptive statistics: probability and meas of central tendency

Question 1

central tendency

Answer 1

• Central tendency indicates the centre of the data and is dependent on the analysis technique used

Question 2

how do you define th central tendency of a distribution

Answer 2

depends on alaysis techniques used which in turn depends on the level of meas of the data

Question 3

____ variables are for categorical differences like gender.

Answer 3

nominal

Question 4

what is the ONLY meas of central tendency for nominal data

Answer 4

mode

Question 5

when applying mode to nominal variable is it possible to have multiple modes or two modes

Answer 5

• can have two modes (bimodal) or be multimodal

Question 6

what level of meas is necessary for calculation of median

Answer 6

data must be rank ordered (ordinal, interval or ratio)

Question 7

what level of meas is necessary for calculation of mean

Answer 7

ONLY if avail data is at interval or ratio leve

Question 8

what is range

Answer 8

• range is difference between max value and min value of a variable

Question 9

which is frequently better meas of central tendency for interval or ratio level data
median or mean

Answer 9

median

Question 10

why is median frequently better meas of central tendency for interval or ratio level data

Answer 10

outliers can distort the data when using mean

Question 11

standard deviation

Answer 11

• standard deviation is avg distance the values fall from the mean.

Question 12

when you have a large Std deviation does t mean there s a small or big spred in values in the data

Answer 12

Lg SD=lg spread

when spread is small most of the avg scores are close to avg score

Question 13

what is inferential statistics

Answer 13

involves associating probabilities with each variable studied

Question 14

what is probability

Answer 14

• Probability is the chance that a particular outcome will occur

Question 15

not sure why they go on abt not being able to say that probabiity is 100% and instead the researcher must say….

Answer 15

the probability approaches 100%?

same thing applies to 0% “the probability approaches 0”

Question 16

what is frequency distribution

Answer 16

lists all possible outome of an experiement and tallies the number of times each outcome occurs. this is then graphed to make easier to understand and see

Question 17

what is probability distribution

Answer 17

• Probability distributon graphs probability of all possible outcomes of the variable rather than their frequency. Eg when rolling dice the probability distribution never changes but the frequency distribution changes depending on the sample

Question 18

if you are rolling dice x1000 and made a frequency distribution of how frequently you roll each number how would it compare to the probabiity distribution of rolling a die indefinitely

Answer 18

when rolling dice the probability distribution never changes but the frequency distribution changes depending on the sample

Question 19

what shape does a normal distribuion have

Answer 19

bell curve

Question 20

in a normal distribution where o you find the mean median and mode

is a normal distribution a type of probability distribution

Answer 20

• Normal distribution ( bell curve) has a probability distribution where the mean median and mode are the same

yes it is

Question 21

o In normal distribution you know __ of its values fall within 1 SD of the mean

Answer 21

68%

Question 22

in normal distribution you know ___ of its values fall within 2 SD of the mean

Answer 22

95%

Question 23

what type of distribution is enerally seen as the most important kind in stats?

Answer 23

normal

Question 24

what are the 2 facts abt normal distrib that make it so important

Answer 24

1-if you take the mean from lots and lots of samples of a pop the distribution of the sample means (the sampling distrib of the mean) becomes normal in the long run. SAMPLING DISTRIBUTIONs plots actual frequencies of a stat vs the range of possible values that statistics can take
2-as you add more and more random variables toether their overall distrib approaches the normal distrib

Question 25

for normal distribtuion Increasing the mean moves the curve shift to the ____ and dec it makes it move ___

Answer 25

o Increasing the mean moves the curve shift to the right and dec it makes it move left

Question 26

if normal distribution what does it do to the shape when you dec the variance? or inc it?

Answer 26

o Dec the variance makes the graph taller and skinnier and inc makes it shorter and fatter

Question 27

t or f any normal variables distribution can be transformed into std normal distribution

Answer 27

true

Question 28

how does a skewed distirbution occur and what is it

Answer 28

• Skewed distribution is an assymeterical distrib of the values of the variable around the mean, making one tail longer than the other
o Skewing isusually d/t lg number of outliers.

Question 29

skewed distribution when outliers are on the right the skew is ____? what about on left?

Answer 29

When outliers are on right then the skew is positive. If on the left its negative

Question 30

t or f

with skewed distribution the mean, median and mode arent the same

Answer 30

o When skewed the mean median and mode aren’t equal

Question 31

what can you use on normally distrib data to see how many standard deviations the observation is from the mean

Answer 31

z score

Question 32

what is a z score

Answer 32

It is a standardized meas that tells you how many SDs the observation is from the mean

Question 33

you have a positive z score what does this mean

Answer 33

o If the value is above the mean or avg itll have a positive z score

Question 34

o The larger the absolute value of the z score the _____ the value is from the avg or mean value in the data set

Answer 34

further

Question 35

what are z scores helpful for

Answer 35

-can be helpful since we know assoc probability 95% of the values fall between 2 std deviations or z scores of approximately -2 to 2+

comparing different data sets eg you get a score of someones ROM exercise (17 and then your z score is -0.5 which would mean their score is worse than avg)

so basically the absolute value of that score doesnt tell us the relationship of the score to the other outcomes/scores

Question 36

how do z scores relate to standard deviation

Answer 36

a z score of 2.0 lies 2.0 std deviations above the mean. While a z score of -0.5 lies 0.5 std deviations below he mean

Question 37

what kind of data can median be used with (level of meas)

Answer 37

ordinal, interval, ratio

Question 38

what two concepts are important in relation to the dispersion of your data

Answer 38

the range

the standard deviation