Collecting Data and standard deviations

Factor increasing accuracy when collecting data

-Ensure samples are random using random number generator

-Make sure there is a large sample size, the more data collected the more precise your results

-representative sample

Normal distribution

-Mean is shown in the middle of the distribution with values either side

-Further removed from the mean, the fewer data points

-How much the data varies from the mean is called standard deviation

standard deviation

-this is a measure of how much values in a sample vary from the mean value. it is useful way of looking at the dispersion of data which takes into account all values collected

-Closer to mean the most extreme deviations are the smaller the standard deviation

Standard deviation core knowledge

-±2 x standard deviation accounts for 95% of the data

-If 2 x SD does not overlap the chances of difference being due to chance is less than 5% therefore the data is significant

-If the SD does overlap the chances of the difference between data being due to chance is more than 5% and therefore the data is not significantly different