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natta225 [31]
3 years ago
11

Which expression represents the number of possible combinations of n items taken r at a time?

Mathematics
2 answers:
denis23 [38]3 years ago
8 0
I would say the equation is

n(r)=?
 because it says taken at 1 time.
mezya [45]3 years ago
8 0

Answer:

^nC_r=\frac{n!}{r!(n-r)!}

Step-by-step explanation:

Given :Total items = n

           Items taken at a time = r

To Find: Which expression represents the number of possible combinations of n items taken r at a time?

Solution:

We will use combination over here.

^nC_r=\frac{n!}{r!(n-r)!}

Now Total items = n

         Items taken at a time = r

Thus expression represents the number of possible combinations of n items taken r at a time is ^nC_r=\frac{n!}{r!(n-r)!}

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Researchers are interested in the effect of a certain nutrient on the growth rate of plant seedlings. Using a hydroponics grow p
Ede4ka [16]

Answer:

1) The mean calculated for this case is \bar X=61.5

2)  61.5-5.4=56.1

3) 61.5+5.4=66.9

4) B. An interval estimate gives us a sense of the accuracy of the point estimate whereas a point estimate alone does not.

Because with the confidence interval we know the confidence level of the interval, and the limits for the parameter at some significance level.  

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

Part 1

In order to calculate the mean and the sample deviation we can use the following formulas:  

\bar X= \sum_{i=1}^n \frac{x_i}{n} (a)  

s=\sqrt{\frac{\sum_{i=1}^n (x_i-\bar X)}{n-1}} (b)  

The mean calculated for this case is \bar X=61.5

The sample deviation calculated s=5.143

\mu population mean (variable of interest)

n=6 represent the sample size  

Part 2

The confidence interval for the mean is given by the following formula:

\bar X \pm ME   (1)

So if we have the margin of error 5.4mm we can find the lowr limit like this:

61.5-5.4=56.1

Part 3

61.5+5.4=66.9

Part 4

B. An interval estimate gives us a sense of the accuracy of the point estimate whereas a point estimate alone does not.

Because with the confidence interval we know the confidence level of the interval, and the limits for the parameter at some significance level.

4 0
3 years ago
Read 2 more answers
What pattern is represented by the polynomial ?
Ymorist [56]

Answer:

choice C. Perfect square trinomial is correct.

Step-by-step explanation:

We need to find the pattern which is represented by the polynomial 4x^2+12x+9.

To find that pattern, we need to factor 4x^2+12x+9

4x^2+12x+9

=4x^2+6x+6x+9

=2x(2x+3)+3(2x+3)

=(2x+3)(2x+3)

=(2x+3)^2

which is a perfect square.

Hence choice C. Perfect square trinomial is correct.

8 0
3 years ago
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