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:
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
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