the probability that a randomly selected day from 2013 will have a group trades total within 85,000 of the mean is 0.1328
Mean (u) = 3421439
Standard deviation = 508638.08
We know that:
z = x-u/sd
Now,
P(u - 85000 <= x <= u + 85000)
u = 3421439
We have to put thus in the formula above
= P(3421439 - 85000 and
3421439 + 85000)
= P(3336439, 3506439)
= (3336439 - 3421439) / 508638.08
,3506439-3421439) / 508638.08)
= prob(-0.1671 and 0.1671
under the z table this is
= 0.5664 - 0.4336
= 0.1328
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