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maths > statistics > Flashcards

statistics Flashcards

1
Q

What is discrete uniform probability?

A

When all the probabilities are the same.

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2
Q

What is a random variable?

A

a variable whose value depends on the outcome of a random event.

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3
Q

What is a discrete variable?

A

A variable that can only take certain numerical values.

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4
Q

What is a sample space?

A

the range of values that a random variable can take

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5
Q

When can you model x with a binomial distribution?

A

when there’s a fixed no.of trials
there’s two possible outcomes
there’s a fixed probability of success
the trials are independent of each other.

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6
Q

What is a population

A

the whole set of items that you’re interested in

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7
Q

What is a census?

A

something that observes or measures every member of a population

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8
Q

What is a sample?

A

it’s a selection of observations taken from a subset of the population which is used to find out info about the population as a whole

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9
Q

What is a simple random sample?

A

A type of sample where the items in the sample are chosen by a random procedure.

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10
Q

what is a systematic sample?

A

A sample where the required elements are chosen at regular intervals from an order list

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11
Q

What is a stratified sample?

A

A type of sample where the population is divided into mutually exclusive strata and a random sample is taken from each

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12
Q

What is quota sampling?

A

A type of sampling where an interviewer or researcher selects a sample that reflects the characteristics of the whole population

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13
Q

What is an opportunity sample?

A

A sample where you ask people that are available at the time of the study and fit the criteria you’re looking for

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14
Q

What are the advantages of using a census?

A

it should give a completely accurate result.

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15
Q

What are the disadvantages of using a census?

A
  1. Time consuming + expensive
  2. cannot be used when the testing process destroys the item.
  3. Hard to process large quantity of data
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16
Q

What are the advantages of using a sample?

A
  1. Less time consuming and expensive than a census.
  2. Fewer people have to respond
  3. less data to process than a census
17
Q

What are the advantages of using a simple random sample.

A

Free of bias
easy and cheap to use for small populations and small samples.
each sampling unit has a known and equal chance of being choosen

18
Q

What are the disadvantages of using a simple random sample?

A
  1. Not suitable when the population size or the sample size is large as it is potentially time consuming disruption and expensive.
  2. A sampling frame is needed
19
Q

what are the advantages of stratified sampling?

A

Sampling accurately reflects the population structure.

guarantees proportional representation of groups within a population

20
Q

What are the disadvantages of using stratified sampling?

A
  1. Population must be clearly classified into distinct strata.
  2. selection within each stratum suffers from the same disadvantages as Simple random sampling
21
Q

What are the advantages of using systematic sampling?

A

Simple and quick

suitable for large samples and large populations.

22
Q

What are disadvantages of using systematic sampling?

A

A sampling frame is needed

it can introduce bias if the sampling frame is not random

23
Q

What are the advantages of using quota sampling?

A

Allows a small sample to still be representative of the population.
No sampling frame needed
quick , easy and cheap
allows for an easy comparison between groups within a population.

24
Q

What are the advantages of using an opportunity sample?

A

Easy to do

Cheap

25
Q

What are the disadvantages of using an opportunity sample.

A

Unlikely to provide a representative sample.

Highly dependent on individual researchers

26
Q

What is a hypothesis?

A

It’s a statement made about the value of a population parameter.

27
Q

What is the null hypothesis?

A

The hypothesis that you assume to be correct

28
Q

What is the alternative hypothesis?

A

It’s the hypothesis tells that you about the parameter if your assumption is shown to be wrong

29
Q

What is a test statistic?

A

The result of the experiment or the statistic that is calculated from the sample

30
Q

What is a significance level?

A

The probability of rejecting the null hypothesis

31
Q

What is a one-tailed test?

A

A hypothesis test with alternative hypotheses in the form H1: p < and H1: p >

32
Q

What is a two-tailed test?

A

A hypothesis test with an alternative hypothesis in the form H1; p not equal to

33
Q

When is a one-tailed test used?

A

When it’s claimed that probability has either gone up or down

34
Q

When is a two tailed test used?

A

When it’s thought that the probability has changed in either direction.

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