Distributions and quality assurance Flashcards
Define ‘probability distribution’
A probability distribution is a list of all possible outcomes together with their probabilities
What notation is used for binominal distribution, and what do the letters represent?
B(n,p)
- n* : number of trials
- p* : probability of success
What conditions must be met for binominal distribution?
- The number of trials is fixed
- The trials are independant
- There are only two possible outcomes for each trial (success or failure)
For binominal distribution, what expresses the probability of n number of trials?
The espansion of (p + q)n, where n = the number of trials
How do you easily expand (p + q)n?
The numbers in front of the p’s and q’s (the coefficients), come from the corrosponding row / follow the pattern of Pascal’s triangle
What is the mean of a binominal distribution?
np
What calculator button can be used to find the coefficients of a binominal expansion?
| nCr |
What conditions must be met to use normal distribution?
- The data is continuous
- The distribution is symmetrical and bell-shaped
- The mode, median and mean are approximately equal
What notation is used for normal distribution, and what do the letters represent?
N(µ,σ2)
- µ* : mean
- σ2 *: variance / standard deviation2
What is the equation for standardised score?
standardised score = (score - mean) / standard deviation
Define ‘quality assurance’
Qulaity assurance involves checking samples to ensure that the product of a manufacturing process meets the required standards
Why are sample means used for quality assurance?
The set of sample means will be more closely distributed than the individual values from the same population
What is a control chart?
A control chart is a time series chart that is used for quality assurance
What are the quality assurance warning limits?
µ + 2σ
µ - 2σ
95% of the sample means should lie between them
What are the quality assurance action limits?
µ + 3σ
µ - 3σ
All of the sample means should lie between them
