Stats

Question 1

What does qualitative data mean

Answer 1

non-numerical data e.g. hair colour

Question 2

What does quantitative data mean

Answer 2

numerical data e.g. number of children

Question 3

discrete data meaning

Answer 3

data that can be counted e.g. number of children

Question 4

continuous data meaning

Answer 4

data that can be measured e.g. height

Question 5

how do you find the class width of a set of data that uses short hand e.g.
length | 1-20 | 21-30 |…

Answer 5

put it into ‘5 < x< 9’ form
e.g. 1 - 20 -> 0.5<x<20.5
then minus 20.5 by 0.5

Question 6

what is descriptive stats?

Answer 6

stats that are collected and organised

Question 7

what is inferential stats

Answer 7

stats where the data is inferred and analysed for conclusion to be made

Question 8

what is a population

Answer 8

a whole set of items that are in interest

Question 9

what is a sample

Answer 9

a selection of items taken as a subset from the population

Question 10

what is a parameter + example

Answer 10

numerical characterists of a population i.e. a mean

Question 11

what is a stat?

Answer 11

a numerical characteristic of a sample that can help to estimate a parameter

Question 12

what tool can you use to remember what a stat and a parameter are used for

Answer 12

stat begins with ‘s’ -> sample
parameter starts with ‘p’ -> Pop

Question 13

what is a census

Answer 13

data that observes and measures every item within the population

Question 14

what is an adv and a dis.adv of a census

Answer 14

adv -
representative of the whole pop

d.adv-
expensive, time-consuming, impossible

Question 15

what can the size of a sample affect

Answer 15

the validity of any conclusions made. The more varied the sample, the more accurate the results

Question 16

what is a sampling frame?

Answer 16

a list with all items of the population individually named

Question 17

what is a sampling unit

Answer 17

an individual unit of the population

Question 18

how do you carry out a simple random sample

Answer 18

1. form a sampling name
2. allocate each item a specific number
3. generate a random number, e.g. using a calculator, as many times as needed for your sample size (if u need a sample size of 30, generate 30 random numbers)

Question 19

how do you carry out systematic sampling

Answer 19

1. form a sampling frame
2. allocate each item a unique number
3. using a calc, generate a random number within your population size (this is your starting unit)
4. calculate the integer component (population size/ sample size = x)
5. select every xth item after the first to be included in the sample

Question 20

how do you carry out stratified sampling

Answer 20

1. divide the data into groups (i.e. year groups, age sex)
2. calculate sample size for strata (xi) -> xi = (sample size/population size) x strata size
3. make sure the sum of all the xi’s equal the sample size (you may have to round is appropriate)
4. conduct a simple random sample for each strata

Question 21

adv and dis adv of
- simple random

Answer 21

adv:
- everyone has an easy chance of being selected - removes bias
- easy to conduct

d.adv:
- time consuming
-

Question 22

adv and dis adv of
- systematic

Answer 22

adv:
- covers a wider study area
- less likely to introduce bias because the starting point is randomly generated

d.adv:
- need a randomly generated starting point
- need to know the number of total pop for it to work

Question 23

adv and dis adv of
- stratified

Answer 23

adv:
- each group receives representation within the sample, as it is proprtional to the group size = increased accuracy

d.adv:
- not all members of the pop may belong to a specific group

Question 24

what are the two non-random techniques

Answer 24

quota sampling
convenience/opportunity sampling

Question 25

what is quota sampling

Answer 25

1. the population is split into groups (year, age, race) 2. individuals are chosen who best fit the requirements

Question 26

what is convenience sampling

Answer 26

1. a sample is taken from people who are availble for the study (i.e. the first 20 people i see)

Question 27

adv and dis adv of quota sampling

Answer 27

adv: - representative d. adv - non random sampling may introduce bias

Question 28

adv and dis adv of convenience/ opportunity sampling

Answer 28

adv: - quick -> no need of a sampling frame d.adv: - not representative -> the first people seen may not effectively represent the whole pop

Question 29

which is affected by extreme values and which arent: mean, media, and mode

Answer 29

mode is not median is not mean is

Question 30

how do you use your GDC to find mean, median, mode, etc

Answer 30

stats -> enter data ->F2 (calc) -> F6 (SET) -> make sure ‘List1’ is the first line and ‘List2’ is the second ->EXIT -> F1 (1-VAR) x = mean n = sample size Med = median Mod = Mode

Question 31

what is the formula for the integer component

Answer 31

population/ sample size P/n

Question 32

what is the formula to find the sample size for strata

Answer 32

sample size for strata = sample size/ population size x strata size xi = n/p x si

Question 33

what is the formula for the mean from a raw list of data

Answer 33

x = sum of the items/ no of items

Question 34

what is the formula for the mean from grouped discrete distribution

Answer 34

x = sum of each item x its frequency/ the sum of the frequencies

Question 35

what is the formula for the mean from grouped continuous distribution

Answer 35

x = sum of the midpoint of each class x its frequency / the sum of its frequencies

Question 36

what is the formula for the median from very large or grouped distribution

Answer 36

n/2 (n = sum of the frequencies)

Question 36

what is the formula for the median of a raw list of data

Answer 36

n+1/2 = the median item

Question 37

what is a quartile

Answer 37

a data point that lies 1/4, 1/2, or 3/4 through the data

Question 38

define range

Answer 38

the difference between the largest and smallest numbers - > easily affected by large valies

Question 39

define interquartile range

Answer 39

the difference between the upper and lower quartiles. shows the spread of the central 50% of data so is unaffcted by outliers

Question 40

define standard deviation

Answer 40

how spread out the data is

Question 41

what is the formula for variance

Answer 41

variance = (standard deviation)^2

Question 42

if you add a constant to the mean and standard deviation, how will they be affected

Answer 42

new mean (xi) = x+c no change to standard deviation

Question 43

if you multiply a constant (b) by the mean and standard deviation, how will they be affected

Answer 43

mean (x) = bx standard deviation (o) = bo

Question 44

what is relative frequency?

Answer 44

the proportion of the total frequency that lies within a class

Question 45

what is the formula for relatiev frequency

Answer 45

class frequency/ sample size this will be a decimal between 0 and 1

Question 46

what does a bell-shaped/ symmetrical distribution suggest

Answer 46

that data is grouped around the mean or median

Question 47

what does a left/negative distribution suggest

Answer 47

data is largely grouped to the top of the range. median is usually higher than mean

Question 48

what does a right/positive distribution suggest

Answer 48

the data is largely grouped towards the bottom of the range. median is usually lower than mean

Question 49

what does a left skewed histogram look like

Answer 49

the highest bars are found on teh right hand side

Question 50

what does a right skewed histogram look like

Answer 50

the highest bars are found on teh left hand side

Question 51

what does unimodal mean

Answer 51

having one peak

Question 52

what does bimodal mean

Answer 52

having two peaks

Question 53

what does uniform mean

Answer 53

where teh frequency for all classes is approximately equal

Question 54

how do u graph a histogram on the gdc

Answer 54

STATS -> enter data -> GRAPH -> SET -> GRAPH 2 = HIST (F6 -> F1) -> set width and starting point -> GRAPH

Question 55

what values do u use when drawing a cumulative frequency graph

Answer 55

use the lower bound value of the first coordinate i.e. if 1.40

Question 56

if a question asks you to find the 80th percentile on a cumulative frequency graph, and it goes up to 160, what do you do?

Answer 56

80/100 x 160

Question 57

what are the 3 equations to calculate outliers

Answer 57

any value which is: - greater than the upper quartile + 1.5 x interquartile range - less than the lower quartile - 1.5 x interquartile range - a value that falls outside the mean + or - 2(standard deviation)

Question 58

what does the box is a box plot show

Answer 58

the middle 50% of data

Question 59

what do the whiskers show

Answer 59

the minimum and maximum values

Question 60

What is bivariate data

Answer 60

data that tracks two characteristics of a population (x and y), called variables

Question 61

what is an explanatory or independent variable

Answer 61

a variable set and controlled by the observer in a study

Question 62

what is the response or dependent variable

Answer 62

a variable recorded to measure the outcome of a study

Question 63

what does association mean

Answer 63

when the explanatory and response variables demonstrate a relationship

Question 64

what does causation mean

Answer 64

when the explanatory/independent variable is the reason for the relationship

Question 65

what is correlation

Answer 65

how well two variables are related

Question 66

what do points closest to a best-fit line mean

Answer 66

closer the points = stronger the correlation

Question 67

what measure can we use to find a numerical value to represent linear correlation

Answer 67

Pearson’s Moment Correlation Coefficient (PMCC)

Question 68

what will the value of the PMCC (r) always be between

Answer 68

-1< r <1

Question 69

if the value of the PMCC is closer to -1 or 1, is it stronger or weaker?

Answer 69

stronger

Question 70

what does y on x mean and x on y mean

Answer 70

y on x => y=ax+b x on y => x=ay+b

Question 71

how do u switch from y on x, to x on y

Answer 71

SET -> swap the 3rd and 4th list around

Question 72

what is interpolation

Answer 72

making an estimate of the response variable for a given explanatory variable ( estimating y, given the x variable), WITHIN the range of data

Question 73

what is extrapolation

Answer 73

making an estimate of the response variable for a given explanatory variable ( estimating y, given the x variable), OUTSIDE the range of data

Question 74

is interpolation or extrapolation more reliable and why

Answer 74

interpolation is more reliable, because extrapolation estimates values outside of the given data, so there is no guarantee a linear trend may continue