Stats and Mechanics

What does a census measure?

Every member of a population

Advantage of census

Accurate result

Disadvantage of census

Expensive/testing may destroy sampling units.

What are sampling units?

The individuals of a population

What is a sampling frame?

A list of the sampling units

What is simple random sampling and how do you do it?

When everything has the same chance of being selected. Use a random number generator/lottery sampling to do it.

Advantage of simple random sampling

Bias free

Disadvantage os simple random sampling

Needs a sampling frame

Is systematic sampling random?

Yes

What is systematic sampling and how do you do it?

Take every x unit. x= population size/sample size. Pick a random number between 1 and k for the starting point.

Advantage of systematic sampling

Quick to use

Disadvantage of systematic sampling

Needs a sampling frame

What is stratified sampling?

Where the sample is representative of the groups (strata) of the population.

Advantage of stratified sampling

Reflects the population

Disadvantage of stratified sampling

Population must be stratified into strata

Is stratified sampling random?

Yes

3 types of random sampling

Simple random, systematic and stratified

2 types of non random sampling

Quota and Opportunity sampling

What is quota sampling?

Like stratified sampling, but the strata are filled by the interviewer/researcher.

Advantage of quota sampling

No sampling frame needed.

Disadvantage of quota sampling

Non-random, potential bias.

What is opportunity sampling?

Where the quota is filled by those available at the time.

Advantage of opportunity sampling

Easy/cheap

Disadvantage of opportunity sampling

Unlikely to be representative

Formula for frequency density

Frequency/Class width

Which 2 things should you compare in data

Location and spread.

What does the pmcc (r) value measure?

The strength of a positive/negative correlation.

What is interpolation?

Estimating inside the data range

What is extrapolation?

Estimating outside the data range

If A and B are mutually exclusive

P(A N B) = 0

If A and B are independent

P(A N B)= P(A) X P(B)

For a discrete uniform distribution…

Probabilities of all outcomes are equal

4 conditions on when to use the binomial expansion

1. When there are fixed number of trials, n

2. When there is a fixed probability of success, p

3. Independent trials

4. There are only 2 outcomes, success or failiure

You can approximate a binomial distribution as a normal distribution, if…

n is large and p is close to 0.5

What is the null hypothesis in hypothesis testing?

H0, what we assume to be true.

What is the alternative hypothesis in hypothesis testing?

H1, what would be true if H0 is wrong.

What is the significant level (in hypothesis testing?)

The given threshold of likeliness

Example of a one tailed test (hypothesis test)

e.g., H1: p<0.5 or p>0.5

Example of a two tailed test (hypothesis test)

e.g., H1: p≠0.5, ensuring the significance level is halved at each end

The null hypothesis for all correlation tests.

H0: p=0

Example of a one tailed test (correlation test)

H1: p<0, p>0.

Example of a two tailed test (correlation test)

e.g., H1: p≠0, ensuring the significance level is halved at each end

What is the test statistic?

The number of successes observed.

What is raw data?

Information obtained from a population.

What are the 5 Uk weather stations of the large data set from bottom to top (South to North)

Camborne, Hurn, Heathrow, Leeming, Leuchars.

What are the 3 international weather stations?

Bejing, Jacksonville and Perth

Which 2 international weather stations are in the northern hemisphere?

Bejing and Jacksonville

Difference between the north vs the south hemisphere

North has summer July-sept. South has winter July-sept.

Patterns for weather in the UK (LDS)

Generally colder in the North

Which UK weather stations are coastal (LDS)?

Camborne, Hurn, Leachars

Which international weather stations are coastal (LDS)?

Perth and Jacksonville

What is daily mean temperature measured in (LDS)?

Degrees celcius

What is daily total rainfall measured in (LDS)?

mm

What is daily total sunshine measured in (LDS)?

hours

What is daily maximum relative humidity measured in (LDS)?

%

What is daily mean visibility measured in (LDS)?

Dm (1Dm=10m)

What is daily mean pressure measured in (LDS)?

hPa (1hPa=100Pa)

What is daily mean total cloud cover measured in (LDS)?

Oktas (0-8)

What is daily maximum gust measured in (LDS)?

Knots or using the Beaufort scale