Answer:
a) 279 b)254
Step-by-step explanation:
Mean = 269 days
standard deviation = 8 days
let n be the pregnancy lenght.
using normal distribution formula
z = (n – mean)/ standard deviation
n = z * standard deviation + mean
Now, z values for the top 12% has to be found using a z table.
The top 12% means 88% of area under the curve. In this case z = 1,176
n = 1,176 * 8 + 269
n = 278.4 = 279
The bottom 3% means 97% of area under the curve. In this case z = -1,882
n = -1,882 * 8 + 269
n = 253.94 = 254
First term: a1 = 151
common difference: d = -14 (we decrease by 14 each time, eg, 151-14 = 137)
nth term of this arithmetic sequence is...
an = a1+d(n-1)
an = 151+(-14)(n-1)
an = 151-14n+14
an = -14n+165
This will be used in the formula below
Sn = n*(a1+an)/2
<span>Sn = n*(151+(-14n+165))/2
</span><span>S26 = 26*(151+(-14*26+165))/2 ... replace every n with 26
</span>S26 = -624
The final answer here is choice C) -624
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</span>
Answer:
11.875
Step-by-step explanation:
Yes so i do need to doing the times and multipics then get a fraction then u will get tot eh answer
The mean = 2,000
s = Sigma ( standard deviation ) = 300
M - 2 s = 2,000- 2 * 300 = 2,000 - 600 = 1,400
M + 2 s = 2,000 + 2 * 300 = 2,000 + 600 = 2,600
Answer.
Useful life of light bulbs within 2 standard deviations of the mean is:
A ) Between 1,400 and 2,600 hours
