Category: Statistics

Understanding the Binomial and Normal Distributions in Biostatistics

Posted on | by Kelvin

 

In this module, you have learned about two of the most frequently used probability distributions in biostatistics: the binomial and normal distributions. The binomial distribution and the normal distribution are similar in several ways. In fact, under certain conditions, the normal distribution is used to approximate the binomial. For your initial post, discuss the following three questions. Provide examples of data that follow each distribution to help illustrate your points.
1. What are the basic differences between the two distributions?
2. Under what circumstances do you think it works well to approximate the binomial using the normal, considering the differences?
3. Under what public health or medical circumstances would it be helpful to identify the probability of an event? Provide some real-life examples.
When responding to your peers, provide clarification where you can and/or ask questions to identify what in their response needs clarification, or provide an additional example of when each distribution could be used that relates to your peer’s example.

 

Making Statistics Accessible: An Explanation for Beginners

Posted on | by Kelvin

 

1. A patient newly diagnosed with a serious ailment is told he has a 60% probability of surviving 5 or more years. Let us assume this statement is accurate. Explain the meaning of this statement to someone with no statistical background in terms he or she will understand.
2. Suppose a population has 26 members identified with the letters A through Z.
a) You select one individual at random from this population. What is the probability of selecting individual A?
b) Assume person A gets selected on an initial draw, you replace person A into the sampling frame, and then take a second random draw. What is the probability of drawing person A on the second draw?
c) Assume person A gets selected on the initial draw and you sample again without replacement. What is the probability of drawing person G on the second draw?
3. Let A represent cat ownership and B represent dog ownership. Suppose 35% of households in a population own cats, 30% own dogs, and 15% own both a cat and a dog. Suppose you know that a household owns a cat. What is the probability that it also owns a dog?
4. What is the complement of an event?
5. Suppose there were 4,065,014 births in a given year. Of those births, 2,081,287 were boys and 1,983,727 were girls.
a) If we randomly select two women from the population who then become pregnant, what is the probability both children will be boys?
b) If we randomly select two women from the population who then become pregnant, what is the probability that at least one child is a boy?
6. Explain the difference between mutually exclusive and independent events.

 

The Mean, Median, and Mode

Posted on | by Kelvin

 

1.) Given the following observations from a sample, calculate the mean, the median, and the mode. Show your work.
8 10 9 12 12
Mean:
Median:
Mode:
2.) Using 500 observations, the following five-point summary was obtained for a variable.
Min Q1 Median Q3 Max
125 200 300 550 1300
a. Interpret Q1 and Q3.
b. Calculate the interquartile range. Determine whether any outliers exist.
c. Is the distribution symmetric? If not, comment on its skewness.
3.) Suppose at the beginning of Year 1 you decide to invest $1,000 in a mutual fund. The following table shows the returns (in %) for the past four years.
Year Annual Return
1 17.3
2 19.6
3 6.8
4 8.2

a. Calculate and interpret the arithmetic mean return.
b. Calculate and interpret the geometric mean return.
c. How much money would you have accumulated by the end of Year 4?
4.) Consider the following population data:
34 42 12 10 22
a. Calculate the range.
b. Calculate MAD.
c. Calculate the population variance.
d. Calculate the population standard deviation.
5.) Consider the following summary measures for the annual returns for Stock 1 and Stock 2 over the past 13 years.
Stock 1: x̄ = 9.62% and s = 23.58%
Stock 2: x̄ = 12.38% and s = 15.45%
a. Which stock had the higher average return?
b. Which stock was riskier over this time period? Given your answer in part (a), is this result surprising? Explain.
c. Given a risk-free rate of 3%, which stock has the higher Sharpe ratio? What does this ratio imply?
6.) Observations are drawn from a bell-shaped distribution with a mean of 20 and a standard deviation of 2.
a. Approximately what percentage of the observations fall between 18 and 22?
b. Approximately what percentage of the observations fall between 16 and 24?
c. Approximately what percentage of the observations are less than 16?

 

One-way and a two-way ANOVA

Posted on | by Kelvin

 

Discuss the differences between a one-way and a two-way ANOVA.
State the assumptions of each one and compare how and why they are different.

Then, analyze how a between subjects’
ANOVA and a repeated measures ANOVA are different from one another. Most importantly, how are the variables different (the amount and type of variables) between the tests?

Next, give a real-world example of when you would use a one-way ANOVA, a two-way ANOVA, and a repeated measures ANOVA. Make sure and state the variables and how they are measured in each example
http://libgen.rs/book/index.php?md5=35DDD99CBA5BD3138D3DC1AEC0438475

Basic Statistics Data Used In Everyday Life

Posted on | by

Present two different types of data, or variables, used in the health field. Examples could be blood pressure, temperature, pH, pain rating scales, pulse oximetry, % hematocrit, minute respiration, gender, age, ethnicity, etc.
Classify each of your variables as qualitative or quantitative and explain why they fall into the category that you chose.
Also, classify each of the variables as to their level of measurement–nominal, ordinal, interval or ratio–and justify your classifications.
Which type of sampling could you use to gather your data? (stratified, cluster, systematic, and convenience sampling)

Long-term morbidity and mortality of overweight adolescents

Posted on | by

 

1. Read the paper by Must, et al (1992): Long-term morbidity and mortality of overweight adolescents. NEJM, 327:1350-55.
Questions Based on the table and formulas below, calculate, label AND state the meaning of your answer (interpret) in a sentence:
Status as Adolescents Number of Participants CHD Deaths Person-years of observation
Overweight 238 40 9,329
Not overweight 270 30 10,980
Risk Ratio = a/(a + b) / c/(c + d)
AR%= (Incidence in exposed – Incidence in unexposed) x 100 ​​​Incidence in exposed

1. Complete the 2×2 table based on the information above: (4 points)

Status as Adolescents CHD Deaths Alive Total
Overweight a b 238
Not overweight c d 270
Total a+c b+d 508
a =
b =
c =
d =
a+c =
​​b+d =
a) The risk of coronary heart disease (CHD) death in participants who were overweight as adolescents and in participants who were not. (8 points)
b) The risk ratio of CHD death associated with having been overweight in adolescence. (4 points)
c) The attributable risk percent for having been overweight in adolescence. Attributable risk estimates the amount or proportion of disease (here: death) that can be attributed to a specific exposure. (4 points)
d) The rate ratio of CHD death for individuals overweight at adolescence compared to lean adolescents. (4 points)
e) The risk difference of CHD death comparing overweight and lean adolescents. (4 points)
2. Based on your calculations, what can you conclude about the effect of being overweight during adolescence on the future risk of coronary heart disease? Decide whether this should be interpreted as “risk of death”. (2 points)
3. Now turn to the Must et al., paper.
a) Compare the crude RR of all-cause mortality associated with overweight in adolescence between men and women in Table 2. What do you conclude? (2 points)
b) Do you think it would be appropriate to show an overall RR of mortality associated with obesity, combining men and women?Explain why or why not. (3 points)

Basic Statistics Data Used In Everyday Life

Posted on | by

 

 

 

 

Present two different types of data, or variables, used in the health field. Examples could be blood pressure, temperature, pH, pain rating scales, pulse oximetry, % hematocrit, minute respiration, gender, age, ethnicity, etc.
Classify each of your variables as qualitative or quantitative and explain why they fall into the category that you chose.
Also, classify each of the variables as to their level of measurement–nominal, ordinal, interval or ratio–and justify your classifications.
Which type of sampling could you use to gather your data? (stratified, cluster, systematic, and convenience sampling)

 

 

 

The Windshield Survey

Posted on | by Brian Leakey

The Windshield Survey includes an assessment of eight community subsystems: physical environment, health and social services, economics, safety and transportation, politics and government, communication, education, and recreation with the purpose of identifying the community health nursing role regarding the needs of the population assessed. Groups will be assigned a community, or municipality.

Each group will conduct a virtual walk-through (drive-thru) assessment of the community, noting evidence of the strengths/weaknesses/resources (city websites, community health departments, census data), develop a nursing diagnosis, and propose community interventions. Your results will be presented in a 20-minute PowerPoint presentation