THIS QUESTION is incomplete (the latter portion appears to be missing; that is, there is no actual Question listed, only relevant, predicating information). Still, I can attempt to answer it because the information supplied appears to be about 80 percent complete.
THE REPORTER'S data, such as it is, will be flawed, even contaminated. He has indeed observed the emergency room for 30 days straight (which is more than a reasonable continuum and time-frame); however -- and this is important -- he has only observed it during the afternoon and during the summer. Any data he collects will, thus, only chiefly pertain to afternoon statistics and summer trends. The output calculated will not (repeat not) be correctly reflective of the most common emergency room injury or condition at the studied hospital. It will, at best, only reveal the most common condition prevalent during the afternoon in the summer months.
IN ORDER TO determine true data, one must always widen the scope of the study and, in particular, seek to collect a relevant sample. [To "show the work," the reporter would simply make tick marks on a standard clipboard, keeping count of all calculated injuries each day. At the end of the 30 days, he would determine a frequency (per day) by dividing each total by 30.]
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