Numerical Descriptive Stats

Question 1

measure of center

Answer 1

value at center or middle of data set

arithmetic mean is a moc obtained by adding/dividing total by # of values

Question 2

mean advantage/dis

Answer 2

advantage= relatively reliable, drawn from same population so don’t vary much, every data value into account

disadvantage= sensitive to every data value so one extreme affect dramatically, not resistant

Question 3

median

Answer 3

middle value when og data values arranged in order of magnitude

IS resistant moc bc not affected by an extreme value

Question 4

mode

Answer 4

value occurs with greatest frequency

can have 1+ or no mode
-bimodal, multimodal

only moc that can be used with nominal data

Question 5

skewed to left

Answer 5

aka negatively skewed

longer left tail

mean and median are to the left of the mode

Question 6

skewed right

Answer 6

aka positively skewed

longer right tail

mean and median to the right of mode

Question 7

measures of variability

Answer 7

range, standard deviation, variance

also called spread or dispersion (how scores differ from one another)

Question 8

range

Answer 8

difference b/t maximum data and minimum value

very sensitive to extreme values so not useful as other mov

measure of variation

Question 9

standard deviation

Answer 9

mov about the mean/average amount of variability,

denoted s or SD

s can inc dramatically w/ inclusion of 1+ outliers

Question 10

variance

Answer 10

mov = square of the SD

Question 11

percentiles

Answer 11

99 percentiles that divide data into 100 groups with 1% of values in each group

Question 12

quartiles

Answer 12

divide ranked values into 4 equal parts w/ 25% in each group

Q1 sep the bottom 25% from top 75%, lower quartile
Q2 same as median so sep bottom 50% from top 50%
Q3 sep bottom 75% from top 25%, upper quartile

Question 13

motivations

Answer 13

measure of relative standing

show location of data values relative to others w/i data set

compare values from different data sets

Question 14

z score

Answer 14

number of SDs that a given value is above/below the mean

mean of z-scores of a population is always 0 and SD of z-scores is always 1

no units

Question 15

independent

probability

Answer 15

if occurrence of one does not affect the probability of the other

Question 16

multiplication rule

Answer 16

used for finding P(A and B) = P(A) * P(B)

A and B are independent

so A occurs in a first trial and B in a second trial

Question 17

continuous random variable

Answer 17

infinitely many possible values

can be associated w/ measurements on a continuous scale w/o gaps or interruptions

i.e baby weight, blood pressure, heart beat

Question 18

calculating z score

Answer 18

given value - mean
/
SD value