<span>n = 5
The formula for the confidence interval (CI) is
CI = m ± z*d/sqrt(n)
where
CI = confidence interval
m = mean
z = z value in standard normal table for desired confidence
n = number of samples
Since we want a 95% confidence interval, we need to divide that in half to get
95/2 = 47.5
Looking up 0.475 in a standard normal table gives us a z value of 1.96
Since we want the margin of error to be ± 0.0001, we want the expression ± z*d/sqrt(n) to also be ± 0.0001. And to simplify things, we can omit the ± and use the formula
0.0001 = z*d/sqrt(n)
Substitute the value z that we looked up, and get
0.0001 = 1.96*d/sqrt(n)
Substitute the standard deviation that we were given and
0.0001 = 1.96*0.001/sqrt(n)
0.0001 = 0.00196/sqrt(n)
Solve for n
0.0001*sqrt(n) = 0.00196
sqrt(n) = 19.6
n = 4.427188724
Since you can't have a fractional value for n, then n should be at least 5 for a 95% confidence interval that the measured mean is within 0.0001 grams of the correct mass.</span>
Answer:
This is a complete lesson with instruction & exercises for 5th grade about multiplying decimals by decimals. The interpretation for multiplying a decimal by a decimal is to think of it as taking a fractional part of a decimal number (the symbol × translates to "of"). The lesson compares multiplication by a decimal to scaling & shrinking a stick. Lastly, it shows the common shortcut to decimal multiplication (multiply as if there were no decimal points; the answer has as many decimals as the factors have in total.)
In the video below, I explain the rule for multiplying decimals (put as many decimal digits in the answer as there are in the factors.) I explain where this rule comes from, using fraction multiplication. The lesson continues below the video.
Answer:
3rd
Step-by-step explanation:
Total of ratio 5+7=12
60/12 = 5
For boys 5x5 = 25 boys in her class
(For girls 7x5 = 35)
You cross multiply
a c
- = -
b d
if ad equals bc, then the fractions are equivalent
