$6x ^2-7x+2=0\\ \\ a=6 , \ b = -7 , \ c=2 \\ \\\Delta = b^{2}-4ac = (-7)^{2}-4*6*2=49-48=1 \\ \\x_{1}=\frac{-b-\sqrt{\Delta }}{2a} =\frac{7-\sqrt{1}}{2*6}=\frac{7-1}{12} =\frac{6}{12}= \frac{1}{ 2}\\ \\x_{2}=\frac{-b+\sqrt{\Delta }}{2a} =\frac{7+\sqrt{1}}{2*6}=\frac{7+1}{12} =\frac{8}{12}= \frac{2}{ 3}$

7 0

4 years ago

When Carson runs the 400 meter dash, his finishing times are normally distributed with a mean of 65 seconds and a standard devia

just olya [345]

Given Information:

Mean time to finish 400 meter dash = μ = 65 seconds

Standard deviation to finish 400 meter dash = σ = 2.5 seconds

Confidence level = 95%

Required Information:

95% confidence interval = ?

Answer:

$CI = 60 \: to \: 70 \: seconds$

Step-by-step explanation:

In the normal distribution, the empirical rule states approximately 68% of all the data lie within 1 standard deviation from the mean, approximately 95% of all the data lie within 2 standard deviations from the mean and approximately 99.7% of all the data lie within 3 standard deviations from the mean.

The confidence interval for 95% confidence limit is given by

$CI = \mu \pm 2\sigma$

Since approximately 95% of all the data lie within 2 standard deviations from the mean. μ is the mean time Carson takes to finish 400 meter dash and σ is the standard deviation.

$CI = 65 \pm 2(2.5)$

$CI = 65 \pm 5$

$CI = 65 - 5 \: to \: 65 + 5$

$CI = 60 \: to \: 70 \: seconds$

Therefore, the 95% confidence interval is between 60 to 70 seconds

What does it mean?

It means that we are 95% confident that the Carson's mean to finish 400 meter dash is within the interval of (60, 70).

4 0

3 years ago