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33 Cards in this Set
- Front
- Back
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What is P(3≤X≤5) the same as |
P(X ≤ 5) – P(X ≤ 2) |
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(nr) =... |
n!/r!(n – r)! |
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When can you model X with a binomial distribution |
Fixed number of trials Two possible outcomes Fixed probability of success Trials are independent of each other |
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What is P(X<7) the same as |
P(X ≤ 6) |
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What is P(X ≥ 7) the same as |
1 – P(X ≤ 6) |
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What is P(X>6) the same as |
1 – P(X ≤ 6) |
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Ads and disads of random sampling (3 ads, 2 disads) |
Ads- free of bias, easy and cheap to implement for small populations and samples, each sampling unit has a known and equal chance of selection Disads- not suitable when population or sample size is large, sampling frame needed |
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Ads and disads of random sampling (3 ads, 2 disads) |
Ads- free of bias, easy and cheap to implement for small populations and samples, each sampling unit has a known and equal chance of selection Disads- not suitable when population or sample size is large, sampling frame needed |
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Ads and disads for systematic sampling (2 for each) |
Ads- simple and quick to use, suitable for large samples and large populations Disads- a sampling frame is nededed, can introduce bias if sampling frame is not random |
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Ads and disads of random sampling (3 ads, 2 disads) |
Ads- free of bias, easy and cheap to implement for small populations and samples, each sampling unit has a known and equal chance of selection Disads- not suitable when population or sample size is large, sampling frame needed |
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Ads and disads for systematic sampling (2 for each) |
Ads- simple and quick to use, suitable for large samples and large populations Disads- a sampling frame is nededed, can introduce bias if sampling frame is not random |
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What is stratified sampling |
Population divided into mutually exclusive strata and a random sample is taken from each |
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Ads and disads of random sampling (3 ads, 2 disads) |
Ads- free of bias, easy and cheap to implement for small populations and samples, each sampling unit has a known and equal chance of selection Disads- not suitable when population or sample size is large, sampling frame needed |
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Ads and disads for systematic sampling (2 for each) |
Ads- simple and quick to use, suitable for large samples and large populations Disads- a sampling frame is nededed, can introduce bias if sampling frame is not random |
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What is stratified sampling |
Population divided into mutually exclusive strata and a random sample is taken from each |
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Ads and disads of stratified sampling (2 each) |
Sample accurately reflects the population structure, guarantees proportional representation of groups within a population Population must be clearly classified into distinct strata, selection within each stratum suffers from same disadvantages of random sampling |
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What is quota sampling |
An interviewer selects a sample that reflects the characteristics of the whole population |
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Ads and disads of quota sampling (3 ads 2 disads) |
Allows a small sample to still be representative of the population, no sampling frame required, quick easy and inexpensive Non-random sampling can introduce sampling, population must be divided into groups which can be costly or inaccurate, |
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Ads and disads of quota sampling (3 ads 2 disads) |
Allows a small sample to still be representative of the population, no sampling frame required, quick easy and inexpensive Non-random sampling can introduce sampling, population must be divided into groups which can be costly or inaccurate, |
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What is opportunity sampling |
Consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for |
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Ads and disads of quota sampling (3 ads 2 disads) |
Allows a small sample to still be representative of the population, no sampling frame required, quick easy and inexpensive Non-random sampling can introduce sampling, population must be divided into groups which can be costly or inaccurate, |
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What is opportunity sampling |
Consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for |
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Ads and disads of opportunity sampling ( 2 each) |
Easy to carry out, inexpensive Unlikely to provide a representative sample, highly dependent on individual researcher |
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How to calculate mean from data in a frequency table |
Sum of the products of the data values and their frequencies/sum of frequencies Products- multiply frequency and value |
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How to calculate mean from data in a frequency table |
Sum of the products of the data values and their frequencies/sum of frequencies Products- multiply frequency and value |
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What do you do if there are intervals |
You get the midpoint and then multiply by frequency |
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Calculating lower quartile for discrete data |
n/4 If whole number- lower quartile is halfway between this data point and the one above Not a whole number- round up |
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Calculating lower quartile for discrete data |
n/4 If whole number- lower quartile is halfway between this data point and the one above Not a whole number- round up |
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And for the upper quartile? |
3n/4 Same rules apply |
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What does mutually exclusive mean |
Cannot happen at the same time |
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If A and B are mutually exclusive how do you figure out the probability of P(AUB) |
P(A) + P(B) |
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What does independent mean |
Not affected by one another |
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How to find the probability of AnB when they are independent |
P(A) x P(B) |
