Question

Question: I can't figure out how to create a pdf f(x) table with the values that match a std of 25 and mean of 110. Also I am using google sheets instead of excel

The solutions to this assignment should be in a word document. Download Classwork normal.docx. Type in the answers and copy in the graphs which you have found using excel. Upload the document as assignment Classwork Normal.

The table below has information about tweeting behavior of two college clubs. The units are characters. For example, the average length of a tweet from the Liberal Club is 110 characters. The lengths are normally distributed.

	Liberal club	Conservative club
Mean	110	80
Standard deviation	20	10
probabilty of cursing in tweet	.25	.10

Sketch the pdf, f(x), for each club.

How do the sketches differ?

For each club find:

Probability the length of a randomly selected tweet is greater than 100 characters

Probability the length is between 75 and 95 characters.

The 90th percentile of the length distribution.

Sketch the cdf, F(x), for each club

In 50 tweets for each club find:

Expected number of tweets that have cursing

The probability that more than 8 tweets with cursing.

Answer 1

How to draw normal distribution in excel , given the mean and standard deviation.

From Chebyshev's inequality we know that 99% of the observation lies with 3 Standard deviation of the data.

Using this we find the upper and lower limit of our data
Upper limit = Mean + 3*SD = 110 + 3*20 = 170
Lower limit = Mean - 3*SD = 110 - 3*20 = 50

Next Put the value of value in excel as show in the screenshot.

We update length from 50 to 170 increase it by 10 at every step.
The probability is found using the excel function called NORM.DIST(X,mean,SD,cummulative)

In this case X is the lenght value.
mean = 110
sd = 20
cummulative = FALSE as we need the probability at each point.

The below screenshot shows the formula used in the excel.

Next use the insert graph function and you will get the Normal distribution as required.