maths data handling yr 1

what is a population

the entire set of items in the group being studied

what is a census

measuring every member of a population

give 1 advantage and 2 disadvantages of a census

adv = accurate

disadvantages:

• expensive

• some testing can destroy the item

what is the list of sampling units called

sampling frame

what are the 3 types of random sampling (names)

• simple random sampling

• systematic sampling

• stratified sampling

what is simple random sampling?

give 1 advantage and 1 disadvantage

equal chance of being selected, use a random number generator alongside a sampling frame

• advantage = free from bias

• disadvantage = sampling frame is required

what is systematic sampling?

give 1 advantage and 1 disadvantage

take every k^th unit, and u pick a starting point between 1 and k using a random number generator

• advantage = quick to use

• disadvantage = sampling frame needed

what is stratified sampling?

give 1 advantage, and 1 disadvantage

proportionally represents the strata (groups) in the sample to reflect the population. uses either systematic or simple random to fill the groups

• advantage: reflects population

• needs clear strata for population

what are the 2 types of non random sampling

• quota sampling

• opportunity sampling

what is opportunity sampling

give 2 advantages and 1 disadvantage

the sample is based on who/what is available when u do it

• advantage = easy

  • cheap

• disadvantage: unlikely to be representative

what is quota sampling

give 1 advantage and 2 disadvantages

is when a quota needs to be filled. not necessarily representative of the population. the groups are filled using opportunity sampling

• advantage: no sampling frame needed

• disadvantage:

  • not random

  • potential bias (as would pick people on if u think they would fill the quota)

what are the 2 equations for the mean

where fx is just the product of the midpoint and the frequency (x = midpoint) (f = freq)

what are the 3 equations for variance?

where the fx is in brackets, so the product is squared

what is the equation for histograms (i want the proportionality one, and the acc full equation one)

when the histogram is a curve what is true for frequency and area

area = freq

can u use calculator ability to find the mean?

yes

can u use the calculator ability to find median / quartiles (if grouped data)

no. will have to do linear interpolation

what does deciles split data into?

into tenths

if you have: y=ax + b, what values affect the mean/quartiles/median (measure of location), and what values affect the standard deviation/variance?

measures of location = both

SD/V = ONLY a

do this question

what are outliers marked with? (on a box plot)

a cross

what is the equation to find upper outlier.

what is it to find lower outlier

for both, assume k = 1.5

upper: Q₃ + 1.5 IQR

lower: Q₁ - 1.5 IQR

what is the acc term/ name when removing anomalies / outliers

cleaning the data

when there is an outlier for a box plot, what are the 2 acceptable ways of plotting the “max” value line? 

where the green one is indicated by the red max upper

and the blue is represented by max blue upper

when comparing box plots, what 2 things must u compare

a measure of spread (IQR or range)

a measure of location (median is best)

when doing cumulative freq diagrams, do u plot against midpoint, or upper boundary

upper boundary

what is on the y axis of a histogram

frequency density

what is the equation that links FD, F, CW

do this question

how do you draw a frequency polygon from a histogram?

the points will be the centre of the top of each bar, and then u connect every single point linearly

for correlation graph, which axis is the independant variable, and which axis is the dependant variable?

independent on x axis

dependent on y axis

what is extrapolation.

it can produce an ____________ result

prediciting a y value (dependent value) using x axis / independent variable outside the given range

an unrelaible result

_______ does not imply ________

correlation does not imply causation