Annie wants to estimate the average number of AP classes a student at her high school takes. She decides to randomly select 6 cl

Answer:

We conclude that the average attention span for teenage boys is less than 5 minutes.

Step-by-step explanation:

We are given that the mean time to distraction for teenage boys working on an independent task was 4 minutes.

Suppose that this mean was based on a random sample of 50 teenage Australian boys and that the sample standard deviation was 1.4 minutes.

<u><em>Let </em></u><u><em> = average attention span for teenage boys</em></u>

SO, Null Hypothesis, : 5 minutes    {means that the average attention span for teenage boys is more than or equal to 5 minutes}

Alternate Hypothesis, : < 5 minutes    {means that the average attention span for teenage boys is less than 5 minutes}

The test statistics that will be used here is <u>One-sample t test statistics</u> as we don't know about the population standard deviation;

                    T.S.  =  ~

where,  = sample mean attention time span for teenage boys = 4 min

             s = sample standard deviation = 1.4 min

             n = sample of teenage boys = 50

So, <u><em>the test statistics</em></u>  =    ~  

                                     =  -5.051

Now at 0.01 significance level, the t table gives critical value of -2.405 at 49 degree of freedom for left-tailed test. Since our test statistics is less than the critical value of t as -2.405 > -5.051, <u>so we have sufficient evidence to reject our null hypothesis as it will fall in the rejection region due to which we reject our null hypothesis.</u>

Therefore, we conclude that the average attention span for teenage boys is less than 5 minutes.

Answer:

  A. Integers

Step-by-step explanation:

Subtraction of whole or natural numbers can result in a negative number that is not in the set. Subtraction of irrational numbers can result in a rational number (√2 -√2 = 0, for example).

Answer:

• 11 nickels
• 5 dimes

Step-by-step explanation:

If all were dimes, she would have $1.60, which is $0.55 more than she actually has. Replacing a dime with a nickel reduces the total by .05, so there must be .55/.05 = 11 such replacements. This is the number of nickels. The number of dimes makes up the rest of the 16 coins.

Nicole has 11 nickels and 5 dimes.

_____

You can write equations for this several ways. My personal favorite is to use a single variable to represent the number of highest-value coin: d = number of dimes. Then the number of nickels is 16-d and the total value is ...

  0.10d + 0.05(16 -d) = 1.05

  0.05d + 0.80 = 1.05 . . . eliminate parentheses, collect terms

  0.05d = 0.25 . . . . . . . . . subtract 0.80

  d = 0.25/0.05 = 5 . . . . . number of dimes

  16-d = 16-5 = 11 . . . . . . . .number of nickels

__

If you let the variable match the number of nickels, the solution looks a lot like the one described in words, above.

  0.05n + 0.10(16 -n) = 1.05

  -0.05n +1.60 = 1.05

  -0.05n = -0.55 . . . . . . . subtract 1.60

  n = -0.55/-0.05 = 11 . . . number of nickels

  16-n = 16-11 = 5 . . . . . . . number of dimes

__

Comparing these two solutions, you see that we work with negative numbers in the second solution. The reason for choosing the variable to represent the higher-value coin is to keep the numbers positive, as they are in the first solution. (It's no big deal, if you're not bothered by negative number arithmetic.)

Answer:

D) x = 4, y = -2, z = 3

Step-by-step explanation:

x = 3z − 5

2x + 2z = y + 16

2(3z - 5) + 2z = y + 16

6z - 10 + 2z = y + 16

8z = y + 26 ---> (A)

7x − 5z = 3y + 19

7(3z - 5) - 5z = 3y + 19

21z - 35 - 5z = 3y + 19

16z = 3y + 54 ---> (B)

8z = y + 26

16z = 3y + 54

2(y + 26) = 3y + 54

2y + 52 = 3y + 54

y = -2

8z = -2 + 26

8z = 24

z = 3

x = 3(3) - 5

x = 4