chapter 8 Flashcards
what is a probability distribution?
a list of all possible outcomes together with their possibilities
what conditions need to be met for binomial distribution to happen?
the number of trials are fixed
the trials are independent
there are two possible outcomes for each trial (success and failure)
what is the mean of binomial distribution?
the number of trials multiplied by the probability of success
what conditions need to be met for binomial distribution to happen?
the data needs to be continuous
the distribution is symmetrical and bell- shaped
the mode, median and mean are approximately equal
what are three important properties of a normal distribution?
68% of observations lie within one standard deviation of the mean
95% of observations lie within 2 standard deviations of the mean
99.8% observations lie within 3 standard deviations of the mean
what is the variance of a normal distribution a good measure of?
a measure of how spread out the data is
what is the formula for number of standard deviations from mean?
value - mean / standard deviation
if you have two sets of data, both modelled by a normal distribution, how can you compare the data?
using standardised scores
what is the standardised score of a data value?
the number of standard deviations above or below the mean that the data lies
what is the formula for standardised scores?
score - mean / standard deviation
if a score is greater than the mean, what will the standardised score be like?
positive
if a score is less than the mean, what will the standardised score be like?
negative
what does quality assurance involve?
checking samples to ensure that the product of a manufacturing process meets the required standards
a set of sample means will be more closely distributed than what?
than the individual values from the same population
when can you construct control charts?
if you take samples at regular time intervals
