Not everyone has to be a six sigma black belt to appreciate and use a well-designed control chart. The top and bottom red lines indicate a standard deviation away, the green line indicates the average, and the black line indicates the values over time. Here's an easy parameterized snippet to generate the chart type:
Title: control_chart(table,value_field,x_axis)
select
[x_axis]
, [value_field]
, average
, average - stdev as stdev_minus_one
, average + stdev as stdev_plus_one
from
[table]
, (
select
avg([value_field]) as average
from
[table]
)
as a
, (
select
stddev_samp([value_field]) as stdev
from
[table]
)
as s