population and samples Flashcards
What are probability distributions?
Series of numbers that give you the expected value for long-run randomness. It is a smaller number of random chance events that may give you a different outcome than you’d expect. Once you have many events, your outcome will be closer to the proportion of events you expected. Looks like a pyramid.
What does the probability of each outcome equal?
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what are the difference between population and samples?
Population parameters (sample mean, standard deviation, variance, observations), if random selection of the population, you have a sample. Samples statistics are sample mean, standard deviation, variance and number of observations, but with different symbols. The population is a set of entities or observations which have the common characteristic. This includes everyone recorded. Sample si a subset of the entities from the population. They are an individual set, which narrow down the records.
What is the sampling distribution?
It is impossible for one person to collect the data for every individual, so you take lots of samples from different countries, and the population will mirror this in some way. You can measure a sample, but not the population.
What is the central limit theorem?
The sample distribution of a sample statistics is the probability distribution that specifies all the possible values. For any distribution with a well-defined mean, variance and standard deviation are normal or non-normal. The means of samples will have normal distribution.
What is the sample mean?
Fluctuates around the true population mean. We can calculate the variability of the sample mean around the population mean. This is because the sampling distribution of the sample mean will be normally distributed, even if the population distribution is not normally distributed.
What is standard error?
This will depend on the sample size. The larger the sample size. The less variability there will be. Standard error on the sample means is population standard deviation divided by the square root of the sample size.
What is the difference between standard error and standard deviation?
Standard deviation describes the spread of a sample, standard error is the measure of precision with which the sample statistic approximates the true population value. The standard error doesn’t estimate any quantity in the population, it measures the uncertainty of a sample representing the population.
When do you use population standard deviation?
When you have the entire population, or you have a sample size of a larger population, but you are only interested in this sample and don’t wish to generalise your findings to the population.
