Stats

Question 1

median is also known as

Answer 1

Q2, second quartile

Question 2

how to calculate the median, and rules for calculating the median

Answer 2

take n and divide it by 2
- if n is a decimal, round up
- if n is a whole number, take an average

Question 3

what does n represent

Answer 3

the sample size

Question 4

how to calculate the mean from raw data

Answer 4

sum of x / n

Question 5

how to calculate the mean from a frequency table

Answer 5

sum of fx / sum of f

Question 6

median
lower quartile
upper quartile equations

Answer 6

• n/2
• n/4
  -3n/4

Question 7

how to find the xth percentile

Answer 7

Px = x * n / 100

Question 8

what is discrete data
what is continuous data

Answer 8

data that takes a finite number of values

continuous takes an infinite number of values

Question 9

examples of continous data

Answer 9

• grouped data
• time

Question 10

rules for discrete data

Answer 10

if you get a decimal number, round up

if you get a whole number, take the average of that number at that position and the number after it

Question 11

rules for continuous data

Answer 11

• check for gaps in the data
• take exact values
• use linear interpelation

Question 12

what to do if your data has gaps

Answer 12

rewrite the frequency classes in boundary form

eg 300 - 349 would be 299.5 - 349.5

Question 13

INTERQUARTILE RANGE

Answer 13

Q3 - Q1

Question 14

How to find the distance between n% to m% (interpercentile range)

Answer 14

Pm - Pn

Question 15

what is the variance and standard deviation of a statistical data

Answer 15

measure the average spread of the data values from its mean value
- variance is a square measure
- standard deviation is the square root of the variance

Question 16

what is random sampling

Answer 16

when each sampling unit in our sampling frame has an equal chance of being chosen in order to avoid bias

Question 17

what is simple random sampling, and what are its advantages and disadvantages

Answer 17

• every sampling unit in sampling frame has equal chance of being selected
• each item in sampling frame has an identifying number
• use random number generator

adv:
- bias free
- easy/cheap to implement
- fair

disadv:
- not suitable when population size is large

Question 18

what is systematic sampling
what are its advantages and disadvantages

Answer 18

• when required elements are chosen at regular intervals in an ordered list

adv:
- simple/quick to use
- suitable for larger samples

disadv:
u need to have a list
- can introduce bias if sampling frame not random

Question 19

how to carry out systematic sampling

Answer 19

• do pop size/sample size
• pick a number from 1 to N
• eg pick 17 out of 50
• select every 50th person. eg 17,67,117

Question 20

what is stratified sampling
hows it carried out
advantages and disadvantagess

Answer 20

• population divided into groups and a simple random sample is carried out in group
• used when sample is large and population naturally divides into groups
• sample size / pop size from each strata

adv:
- reflects population structure
- guarantees proportional representation of groups within population

disadv:
-population must be clearly classified into distinct strata
- selection within each strata suffers from the same disadvantages as simple random sampling

Question 21

why would random sampling be problematic

Answer 21

might not know the sampling frame

Question 22

non random sampling - quota sampling
adv and disadv

Answer 22

• divide population into groups according to characteristic of interest
• choose people within each group via suitable means until the quota for each geoup is filled

adv - allows small sample to still be representative of population
- no sampling frame required
- quick, easy, inexpensive
- allows for easy comparison between different groups in population

disadv - non random sampling can introduce bias
-population must be divided into groups, can be costly or inaccurate
- increasing scope of study increases number of groups, adding time/expense
- non responses are not recorded

Question 23

non random sampling - opportunity/convenience sampling

Answer 23

• sample taken from people who are available at the time of study
• interviewer selects the actual sampling units according to the set criteria

adv
- easy and inexpensive to carry out
disadv
- unlikely to provide a representative sample
- highly dependent researcher

Question 24

types of data

Answer 24

• qualitative/categorical - non numerical values
• quantitative- numerical data
• discrete - can only take specific values eg shoe size - part of quantitative
  continuous - can take any decimal value - part of quantitate

Question 25

locations of the 5 uk weather stations 3 international weather stations

Answer 25

UK - Heathrow - Camborne - on the coast - Hurn - on the coast - Leeminh - Leuchars - on the coast INTERNATIONAL - Beijing - northern - Jacksonville - hot /tropical florida lots of hurricanes and tornadoes - northern - Perth - southern hemisphere

Question 26

difference between northern and southern hemisphere

Answer 26

when northern is in winter southern is in summer and vice versa

Question 27

rules for events which are independent

Answer 27

Two events 𝐴 and 𝐵 are independent if the occurrence of one event does not affect the probability of the other. This means: AnB = P(A) . P(B) - The probability of both events occurring is the product of their individual probabilities. - Independent events can overlap—they are not necessarily disjoint

Question 28

rules for mutually exclusive events

Answer 28

- Two events 𝐴 and 𝐵 are mutually exclusive if they cannot both occur at the same time. This means: AnB = 0 and P(AUB) = P(A) + P(B)

Question 29

why might you include an outlier in the readings and why might you not include it

Answer 29

- because it is still part of the distribution data - it might be unlikely to be an anomaly - but it is an outlier so may not be representative of the typical data - it might be a mistake

Question 30

in y = a + bx, what do the coefficients represent

Answer 30

- the coefficient b tells you the change in y for each unit change in x

Question 31

what is interpolation (scatter diagram) and what is extrapolation

Answer 31

- interpolation is making a prediction based on a value inside the range - extrapolation is making a prediction based on a value outside the range, and gives a less reliable estimate

Question 32

how predictions are made with scatter diagrams

Answer 32

- only make predictions for the dependent variable - the independent variable is used to make the prediction

Question 33

how else can u work standard deviation

Answer 33

root sxx / n

Question 34

When to use each type of distribution?

Answer 34

🎲 Uniform Distribution Use when: All outcomes are equally likely Each value has the same probability You're dealing with random, fair selections (e.g. dice rolls, spinning wheels, choosing a number at random) 🔁 Example: Choosing an integer between 1 and 9 at random → Each number (1–9) has probability = 1/9 📊 Non-Uniform Distribution Use when: Some outcomes are more likely than others You’re given a frequency table or probabilities that are not equal There’s real-world data involved (e.g. survey responses, test scores) Example: A table showing how many kids picked each number from 1 to 9 — some numbers are chosen more often