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The life times of light bulbs produced by a particular manufacturer have a mean of 1,200 hours and a standard deviation of 400 h

Nezavi [6.7K]

Answer:

a. 1200hours

b. σ² = 400² =160000hour

c. standard error = 133.33

d. for 9 lightbulb it is likely that 9*0.146 = 1.31 bulbs will have lives of fewer than 1,050 hours?

Step-by-step explanation:

mean of 1,200 hours

σ, a standard deviation of 400 hours.

Sample size, N = nine bulbs,

a) mean of the sample mean lifetime: is given as 1,200 hours

b) variance of the sample mean is the square of the σ, a standard deviation of 400 hours.

σ² = 400² =160000hours

c) What is the standard error of the sample mean?

The standard deviation of a sampling distribution of mean values is called the standard error of the means,

standard error of the means, σx = σ √N

The formula for the standard error of the means is true for all values infinite number of sample, N.

σx = σ √N

=400 √9 = 400/3 =133.3333

d) the probability that, on average, those nine lightbulbs have lives of fewer than 1,050 hours

The area under part of a normal probability curve is directly proportional to probability and the value is calculated as

z = ( x₁−x) /σ

where z = propability of normal curve

x₁ = variate mean = 1050hours

x = mean of 1200hours

σ = standard deviation = 400

applying the formula,

z= (1050-1200)/400

z = 150/400 =0.375

Using a table of partial areas beneath the standardized normal curve (see Table of normal curve, a z-value of 0.375 corresponds to an area of 0.1460 between the mean value.

Thus the probability of a lightbulbs having lives of fewer than 1,050 hours is 0.1460.

for 9 lightbulb it is likely that 9*0.146 i.e. 1.31 bulbs will have lives of fewer than 1,050 hours?

8 0

3 years ago

Form a sequence that has two arithmetic means between -13 and 89. a. -13, 33, 43, 89 c. -13, 21, 55, 89 b. -18, -36, -72, -144 d

iogann1982 [59]

Form a sequence that has two arithmetic means between -13 and 89. a. -13, 33, 43, 89 c. -13, 21, 55, 89 b. -18, -36, -72, -144 d. -18, -81, -144

Solution:

Since it has to be between -13 and 89, letter d and b are not anymore considered to be the answer.

for a:
33-(-13)=46=d
43-33=10=d the value for this d is different from the two sequence,
89-43=46=d
they have different value for d, thus this is not the answer!

for c:
21-(-13)=34=d
55-21=34=d
89-55=34=d

they have the same value for d, thus the correct answer is c. -13, 21, 55, 89

8 0

4 years ago

Find the distance between the points given. (-3, 2) and (9, -3)

g100num [7]

The distance will be given by the equation;
D= $\sqrt{( x_{1} - x_{2} )^{2} +( y_{1} - y_{2} )^{2} }$
D= $\sqrt{ (-3-9)^{2}+( 2--3)^{2} }$
D= $\sqrt{ (-12)^{2} + (5)^{2} }$
D= $\sqrt{169}$
D=13 units

8 0

3 years ago

With the drain open, a pool loses water at a rate of 9 gallons per minute. At that rate, how long will it take to drain 486 gall

Snezhnost [94]

divide 486 by 9 = 54

it would take about 54 minutes

8 0

3 years ago

Triangles abc, dbe, and fbg are all symmetric about the y-axis. what are the coordinates of the centroid?

Drupady [299]

Answer:

The coordinates of the centroid are (0, 5)