Transcript Presentation

Is it radioactive or not?
How scientists and
mathematicians decide if
measured quantities are different
or not.
Distribution of Measurements
Repeated measured
values are never
identical.
Typically distributed
symmetrically
about the mean
Standard deviation
(SD) is a measure
of the spread of
measured values
“Normal” distributions
68% of
measured
values within
1 SD of the
mean
95% of
measured
values with 2
SD of the
mean
Comparing measurements



Background measurements are
normal distribution
Activity measurements are normal
distributions
How to decide if the distributions are
the same or different?
Comparing two data sets



Background – low mean
“sample” – high mean
95% certain different if means are 2
SD apart.
Comparing two data sets

Same if means are not 2 SD apart.
How to check without graphs?
Number lines




Label the means of both distributions
Mark mean1 – 2 SD1 & mean1+2 SD1
Mark mean2 – 2 SD2 & mean2+2 SD2
If the two distributions overlap, they
are not different