What is the formula for working out the mean in a frequency table?
x̄ = Σfx / Σf
When estimating the mean in a grouped frequency table, what is x?
The midpoint.
How is the midpoint calculated?
(lower limit + upper limit) / 2
When estimating the mean in a grouped frequency table, what is x?
The midpoint.
How is the midpoint calculated?
(lower limit + upper limit) / 2
What is the formula for working out the mean in a histogram?
x̄ = Σfx / Σf
When estimating the mean in a histogram, what is x?
The midpoint.
What is the formula for working out the position of the median in a histogram?
position of the median = Σf / 2
How do you work out the estimation of the median in a histogram?
- Work out the cumulative frequency of the data.
- Work out the position of the median.
- Calculate (the position of the median - the cumulative frequency of the group before).
- Calculate (step 3 / frequency of group containing median.)
- Calculate (step 4 x class width)
How can you tell that the skew is positive?
mode < median < mean
How can you tell that the skew is negative?
mean < median < mode
How can the mean of percentage changes be found?
- Work out the decimals of the percentages.
- Multiply decimals.
- n root step 2.
- Multiply step 3 by 100.
- Subtract 100 from step 4.
What is a suitable average for a symmetrical histogram?
The mean because it is affected by extreme values.
What is a suitable average for a positively skewed histogram?
The median because it is not affected by extreme values.
What is a suitable average for a negatively skewed histogram.
The median because it is not affected by extreme values.
What is the purpose of a quality assurance chart?
To monitor the process so that it can be stopped if the values go outside of an allowable range or mean.
