Sometimes your system may display an error code indicating that the standard error specified for the trust level is 99. There can be several reasons for this error to occur.
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SE is (upper limit – greatly reduce the limit) / 3.92. For 90% confidence points, divide by 3.29 instead of 3.92; for 99% confidence intervals you always divide by 5.15.
We measured the height of 46 randomly selected men and got their average height of 175 cm
Of course we know that the normal size change for men is 20 cm.
95% confidence interval (we’ll show you how to calculate it later):
Methods “±” means “more or less”, so 175 cm ± 6.2 cm
Our result is that ALL men (if any of us can measure all heights) are likely to be between 168.8cm and 181.2cm.
The “95%” think that 95% of the searches we’ve just run yield a true average, and 5% don’t.
Therefore, there is a 1 in 20 (5%) absolute chance that our confidence interval does not include a particular mean.
Note. We must use the standard deviation for the entire population, butin many cases we won’t know.
We can use the standard deviation of my sample if we have enough observations (maximum n = 30, hopefully more).
The value after all ± is called the margin of error
Example: Apple Orchard
There are hundreds of apples on the trees, so customers randomly choose only 46 apples and get: