They studied the number of cases over a 229-day period from May 1 through Dec. 15 and divided the results of the two study groups by days with mask mandates and days without mask mandates. The non-mandate data group includes both states that never had a mandate and those that did at some point, but data set included only the days they did not have a mask mandate.
The results: When comparing states with mandates vs. those without, or periods of times within a state with a mandate vs. without, there is absolutely no evidence the mask mandate worked to slow the spread one iota. In total, in the states that had a mandate in effect, there were 9,605,256 confirmed COVID cases over 5,907 total days, an average of 27 cases per 100,000 per day. When states did nothave a statewide order (which includes the states that never had them and the period of time masking states did not have the mandate in place) there were 5,781,716 cases over 5,772 total days, averaging 17 cases per 100,000 people per day.