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damaskus [11]
3 years ago
7

The life of a certain brand of battery is normally distributed, with mean 128 hours and standard deviation 16 hours. What is the

probability that a battery you buy lasts at most 100 hours? Standardize the variable.
Mathematics
1 answer:
Katyanochek1 [597]3 years ago
7 0

Answer:

x = 100 is equivalent to z = -1.75

Step-by-step explanation:

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There were 2430 Major League Baseball games played in 2009, and the home team won the game in 53% of the games. If we consider t
Ivahew [28]

Answer:

z=\frac{0.53 -0.5}{\sqrt{\frac{0.5(1-0.5)}{2430}}}=2.958  

p_v =P(Z>2.958)=0.0015  

So the p value obtained was a very low value and using the significance level given \alpha=0.05 we have p_v so we can conclude that we have enough evidence to reject the null hypothesis, and we can said that at 5% of significance the proportion is significantly higher than 0.5 .  

Step-by-step explanation:

1) Data given and notation  

n=2430 represent the random sample taken

\hat p=0.53 estimated proportion when the home team won the game

p_o=0.5 is the value that we want to test

\alpha=0.05 represent the significance level

Confidence=95% or 0.95

z would represent the statistic (variable of interest)

p_v represent the p value (variable of interest)  

2) Concepts and formulas to use  

We need to conduct a hypothesis in order to test the claim that the proportion is higher than 0.5 or 50%:  

Null hypothesis:p\leq 0.5  

Alternative hypothesis:p > 0.5  

When we conduct a proportion test we need to use the z statistic, and the is given by:  

z=\frac{\hat p -p_o}{\sqrt{\frac{p_o (1-p_o)}{n}}} (1)  

The One-Sample Proportion Test is used to assess whether a population proportion \hat p is significantly different from a hypothesized value p_o.

3) Calculate the statistic  

Since we have all the info requires we can replace in formula (1) like this:  

z=\frac{0.53 -0.5}{\sqrt{\frac{0.5(1-0.5)}{2430}}}=2.958  

4) Statistical decision  

It's important to refresh the p value method or p value approach . "This method is about determining "likely" or "unlikely" by determining the probability assuming the null hypothesis were true of observing a more extreme test statistic in the direction of the alternative hypothesis than the one observed". Or in other words is just a method to have an statistical decision to fail to reject or reject the null hypothesis.  

The significance level provided \alpha=0.05. The next step would be calculate the p value for this test.  

Since is a right tailed test the p value would be:  

p_v =P(Z>2.958)=0.0015  

So the p value obtained was a very low value and using the significance level given \alpha=0.05 we have p_v so we can conclude that we have enough evidence to reject the null hypothesis, and we can said that at 5% of significance the proportion is significantly higher than 0.5 .  

8 0
3 years ago
A rock is dropped from a bridge 320 feet above the river. The pathway that the rock takes can be modeled by the equation h= -16t
Marina86 [1]

Answer:

The rock will take about 4.5 seconds to reach the river

Step-by-step explanation:

* lets study the situation of the rock

- The rock is dropped means the initial velocity is zero

- The motion is free fall under earth gravity

- The rock dropped from a bridge 320 feet above the river

- The equation of the pathway is h = -16t² + 320

- When the rock reach to the ground the height will be zero

* Now lets substitute h by zero in the equation to find t

∵ h = -16t² + 320

∵ h = 0

∴ 0 = -16t² + 320 ⇒ add 16t² to both sides

∴ 16t² = 320 ⇒ divide both sides by 16

∴ t² = 320/16 = 20

∴ t² = 20 ⇒ take √ for both sides

∴ t = √20 = 2√5 ≅ 4.5 seconds

* The rock will take about 4.5 seconds to reach the river

4 0
3 years ago
Every person in a certain group is either a Dodgers fan or a Yankees fan, but not both. The ratio of Yankees fans to Dodgers fan
Deffense [45]

Answer:

  E)  176

Step-by-step explanation:

The difference in ratio units is 5 -3 = 2. If one ratio unit changes sides, the ratio will be 4 : 4, or 1 : 1. Then one ratio unit represents 22 group members.

There are a total of 5+3 = 8 ratio units, so there are ...

  8 × 22 = 176

people in the group.

_____

<em>Check</em>

The original group has 5 × 22 = 110 Yankees fans and 3 × 22 = 66 Dodgers fans, for a total of 110+66 = 176 group members. If 22 switch sides, there will be 110-22 = 88 Yankees fans and 66+22 = 88 Dodgers fans, making the ratio ...

  88 : 88 = 1 : 1

7 0
3 years ago
The ratio of the number of apples to the number of pears in a basket was 3:5. After 7more apples were added to the basket and 9
atroni [7]

Answer:

Apples = 24

Pears = 40

Step-by-step explanation:

Let u be the unit of fruit in the basket,

number of apples: 3u +7

number of pears: 5u -9

now to find u, we equate the two equations.

3u+7=5u-9

Now simplify.

5u-3u=7+9

2u=16

u=8

Now we can find the original number of apples and pears by substituting u.

so original number of apples = 3u = 3(8) = 24

and original number of pears = 5u = 5(8) = 40

5 0
3 years ago
Jamie took an 8-week keyboarding class. At the end of each week, she took a test to find the number of words she could type per
Bingel [31]
She improved about 4.3 words per min each week
6 0
3 years ago
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