SOCI 3311 Blog

Open the z/percentile rank calculator.

Enter 25 as the percentile rank and click CALCULATE. The calculator will give you the z score.

Part 2 is asking for the z score with 40% of observations above it. This would be the same z score with 60% of the observations below it. Since percentile rank is defined as the percent of score below, enter 60 into the z/percentile rank calculator as the percentile rank. Click CALCULATE and the calculator will give you the z score.

ALSO: See COMMENT on previous BLOG entry.

How do we approach this problem?

what does it mean to describe the distribution of scores? do you use positive negative normal?

I thought a list of U.S. senators would be considered a population; however, I took a practice true false quiz and number 13 says that a list of the world's billionaires would be considered a parameter. So is a list of a population a parameter?

If the midpoint of a class interval (interval width=11) is 15, the upper limit of the interval is _____.

Think of a class interval with 11 values that we will represent as an underline character:

_ _ _ _ _ _ _ _ _ _ _

Now we know the middle value is 15, so place 15 in the middle:

_ _ _ _ _ 15 _ _ _ _ _

To find the upper limit, simply add the values to the RIGHT of the midpoint:

_ _ _ _ _ 15 16 17 18 19 20

The upper limit is 20.

Could you also find the lower limit?

I'm having a hard time with this one. it seems impossible. what am I missing?

Before I submit the assignment I want to double check something (we are graded on correctness right?). Do we assume Hair Color as limited to black, brown, blonde, red or consider in reality all the different shades of brown, blonde, and red hair? If assume black, brown, blonde or red, then it is discrete, but if consider all the shades, then continuous I believe. Thanks!

The UNIT LABEL is the word or phrase that describes what the numbers represent.

Do the numbers represents years, calories, pounds, students, etc?

Look for the word that follows the numbers. That will almost always be the UNIT LABEL.

What is meant by the unit label??

Does anyone know how to copy the stem plot to the homework or do we have to just make our own. I tried it and another weird object came up

Assignment 2 - 7

For this problem, you will first need to convert the raw scores to z form and then read area under the standard normal curve.

For example, to convert 134 to z form we would have:

z = (134-125)/10 or 9/10 = .9

Now read the area ABOVE z=.9. Remember, when reading area above, you must substitute a real value for infinity. So enter as your two z scores, .9 and 5.

Area equals .1841.

Finally, multiply this area by 100 to convert it to a percent.

Final answer: 18.41%

10:

1. Convert 100 to z form and read the area above this z score. Multiply the area times 100 to convert it to a %. z = (100-110)/25 or 10/25 = -.4. Now read the area ABOVE this z score using the standard normal calculator and multiply this area times 100 to convert it to a %.

2. Convert 150 to z form and read the area above this z score. Multiply the area times 100 to convert it to a %. z = (150-110)/25 or 40/25=1.6. Now read the area ABOVE this z score using the standard normal calculator and then multiply this area times 100 to convert it to a %.

3. Find the z score associated with the highest 25% (hint: this is the same z score as the lowest 75% or a percentile rank of 75). Hence use the z/percentile rank converter calculator enter 75 as the percentile rank and click CALCULATE to find z.

Once you have z, substitute z, μ, and σ into the formula for z and solve for X.

The z associated with a percentile rank of 75 is .67.

Hence substitute .67 for z.

Substitute 110 for μ.

Substitute 25 for σ.

Solve for X

Z = (X - μ)/σ

With substitution:

.67 = (X - 110)/25

You are solving for the value of X.

The Stem Plot needs to appear in your journal for grading purposes.

Are we supposed to copy and paste the stem plot on our journals? Or is it for observation only for the next question??

In assignments 2 and 3, you may need a few GREEK symbols.

Here's how to get them.

Type & s i g m a ; (I've included spaces here to show you the exact string of characters needed BUT NO SPACES when you type it) to get σ. PLEASE NOTE: You MUST include the & and the ;

Type & m u ; (I've included spaces here to show you the exact string of characters needed BUT NO SPACES when you type it) to get μ. PLEASE NOTE: You MUST include the & and the ;

Type & s u m ; (I've included spaces here to show you the exact string of characters needed BUT NO SPACES when you type it) to get ∑. PLEASE NOTE: You MUST include the & and the ;

In other words, the & and ; are part of the string.

& s i g m a ; (no spaces please) = σ

& m u ; (no spaces please) = μ

& s u m ; (no spaces please) = ∑

& a l p h a ; (no spaces please) = α

& n e ; (no spaces please) = ≠

& p l u s m n ; (no spaces please) = ±

If you have questions, just let me know.

If you are asked to read area under the standard normal curve, use the STANDARD NORMAL CURVE calculator.

This calculator requires 2 z scores and you are reading the area between z boundaries.

When asked to read the area ABOVE a given z (or to the right of a given z), your second boundary is technically infinity. However, we will need to substitute a number for infinity. Please use the number 5 (or any number larger than 5). This is because virtually 100% of the area lies between z = -4 and z = 4. Hence any number greater than 4 will give us 4 digits to the right of the decimal of accuracy.

Likewise, when asked to read the area BELOW a given z (or to the left of a given z), use -5 (or any number smaller than -5).

Hello Everyone, On the homework assignment 1...number 2and 5, where do we get the vocabulary words to put in the missing space?

To SUMMARIZE the data, you will need to look at the SHAPE of the distribution. To do this, you need to mentally rotate the stem plot 90 degrees in a counter clockwise direction.

Notice this plot displays a positively skewed distribution -- with the bulk of scores on the low end of the distribution and fewer scores on the high end of the distribution.

Knowing what the scores represent, can you make a summary statement?

I am a bit confused on 6-3. about summarizing the data.

A quantitative frequency distribution should include the following columns:

Class Intervals | Absolute Frequencies | Cumulative Absolute Frequencies | Relative Frequencies | Cumulative Relative Frequencies

Beginning with 1 and using an interval width of 10, we would have the following class intevals:

Class Intervals

1-10
11-20
21-30
31-40
41-50
51-60
61-70
71-80
81-90

Now create the absolute frequencies column by COUNTING the number of raw data values that are located in each class interval:
Intervals aF
1-10 9

.... and so on.

Please see Unit 2 on creating the remaining columns as well (caF, rF, crF).

Education measured in YEARS

YEARS is the key word here. Years is a continuous variable. Hence, the correct answer is CONTINUOUS.

#3-2 Is asking whether Education (measured in years) is discrete or continuous. Is this referring to 2-year schools and 4-year schools? I ask this because that makes it a set but in reality someone can go to school their whole life if they choose to. I am confused on the question.

Because students are still adding/dropping classes, I am waiting until Monday to load the quizzes. You should see all 5 quizzes (under MY EXAMS) Monday morning.

When completing the graded homework assignments, it is not necessary to rewrite the questions.

IN FACT, PLEASE DO NOT REWRITE THE QUESTIONS. Just enter your answers using the same numbering system as listed with the questions.

For example, for Homework assignment 1, Question 1, your journal entry should appear as follows:

1-1. parameter
1-2. population
1-3. population
1-4. statistic
1-5. sample