BIOL 202 Lecture Notes - Lecture 1: Statistic, Standard Deviation

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28 May 2018

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LAB 1: EXPERIMENTS AND EXCEL

Name: Isbah Afzal

Class: BIO202-008

Circle the correct answer, or provide a short (two word) answer to each question below:

1. There are two hospitals in a town. One of them is smaller than the other. 70% of

the babies born a particular day are boys at one hospital and 50% of the babies

born on that day were from the other hospital. Which hospital was most likely to

be the smaller hospital, the one with 70% boys or the one with 50% boys?

Answer: 70% is smaller.

2. The true population mean is known. You take a random sample from that

population of sample size 10 and another sample of sample size 20. Which sample

mean (N=10 or N=20) do you expect to be closest to the true population mean? Is

this guaranteed to be true?

Answer: N=20 will be closer to the true population mean. It is not guaranteed to

be true.

3. What happens to the sample mean as the sample size increases? Does it get closer

or farther away from the true population mean in a biological population? Is this

guaranteed to happen as the sample size continues to increase?

As the sample size increases → the standard deviation of the means decreases.

As the sample size increases → the sample mean gets closer to the true population

mean in a biological population.

Yes, according to the law of large numbers, as a sample size grows, its mean gets

closer to true population.

4. Why are considerations of sampling error important?

It is important to consider the sampling error because it tells us the difference

between the sample statistic used to estimate the true population and the actual

parameter whose value is unknown to us.

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Document Summary

Circle the correct answer, or provide a short (two word) answer to each question below: there are two hospitals in a town. One of them is smaller than the other. 70% of the babies born a particular day are boys at one hospital and 50% of the babies born on that day were from the other hospital. Answer: 70% is smaller: the true population mean is known. You take a random sample from that population of sample size 10 and another sample of sample size 20. Answer: n=20 will be closer to the true population mean. As the sample size increases the standard deviation of the means decreases. As the sample size increases the sample mean gets closer to the true population mean in a biological population.

Related Questions

In this first exercise, we are going to look for evidence of evolutionary change in a population in the absence of natural selection by looking at the change in allele frequencies over time in a simulated population. We will start with a population of 50 individuals in which there are two alternate alleles (H and h) in equal proportions (each at a frequency of 0.5 or 50%). Individuals have the possible genotypes: HH, Hh or hh. These two alleles do not offer any selective advantage, so neither is selected for or against, meaning they are neutral. We will record the frequency of these alleles over 10 generations. Prior to advancing on to the next generation, six alleles (= three individuals) will be removed at random.

Before you begin, answer the following:

Question

What is your prediction as to what will happen to the frequencies (note that this is different than the number) of these two alleles over 10 generations? Keep in mind that there is no selective advantage of one allele over the other. Be sure to word your prediction as an âif-thenâ statement based on the experiment design. (1 pts).

5. After going for a swim in a pond on uncle Leroy's farm, you realize one of the snozzlewhompin scratches you received the day before is rather nicely infected, oozing a yellowish-green pus and smelling somewhat similar to Trader Joe's White Cheddar Popcorn. Since the closest medical facility is a day and half from uncle Leroy's farm, you decide to see what the microbe it is that has infected your scratch by examining a sample under the microscope. Upon examination, you discover that you are infected with a rare amoeboid critter that divides via mitosis every 60 minutes. Assuming a single amoeba initiated the infection, estimate the population size considering that it has been 24 hours since your swim.

a) Alarmed by the geometric growth you calculated above, you a do a bit of research on the ol' interwebs (I know, hard to believe uncle Leroy has access, right!) and discover that the amoeba infecting you reaches a lethal concentration at approximately 1.0 x 1010 cells, and has an intrinsic rate of increase (rm) of 0.7 per hour. Given this information, how long (in hours) will it be from the initial infection until the amoeboid population reaches a fatal concentration? Think you'll survive?

b) There are 4 biological processes that contribute to growth (or reduction) in population density. In the models of population growth you used to answer 5 and 5a, which two of these processes have you accounted for? What are the two you have you ignored?

1. The risk of acquiring disease is measured by the

a. Incidence rate

b. Incidence rate times the average duration of the disease

c. Incidence rate divided by the prevalence rate

d. Prevalence rate

e. Prevalence rate times the average duration of the disease

2. The strength of an association between a factor and a disease is best measure by .

a. Incubation rate

b. Incidence of the disease in the total population

c. Prevalence of the factor

d. Attributable risk

e. Relative risk

3. Case fatality rate for a given disease refers to

a. The crude mortality rate per 100,000 population

b. Cause-specific mortality rate due to the disease

c. A fatal outcome of any disease

d. The percentage of deaths among cases of the disease

e. The proportion of deaths due to the disease among all deaths from all causes

4. An investigator is interested in etiology of neonatal jaundice. To study this condition, he selected 100 children who were diagnosed with this condition and 100 children born in the same period and in the same hospital who did not have a diagnosis of neonatal jaundice. He then reviewed the obstetrical and delivery records of their mothers to determine various prenatal and perinatal exposures. This is an example of a(n):

a. Cross-sectional study

b. Case-control study

c. Cohort study

d. Clinical trial

e. Experiment

5. Which of the following statements describes the major advantages of a randomized clinical trial?

a. It avoids observer bias

b. It lends itself to ethical justification

c. It yields results replicable in other patients

d. It rules out self-selection of participants to the different treatment groups

d. It enrolls representative patients

6. A survey conducted in England revealed that of 224 families in which there had been a known case of poliomyelitis, 56 maintained parakeets as a family pet. In another British survey, 30 out of 99 poliomyelitis patients questioned kept parakeets. The inference that there is some relationship between the presence of a parakeet in a household and the occurrence of poliomyelitis among household members is

a. Correct b.

Incorrect because of failure to distinguish between incidence and prevalence

c. Incorrect because a proportionate ratio is used when a rate is required to support the inference

d. Incorrect because a failure to recognize a possible cohort phenomenon

e. Incorrect because there is no control or comparison group.

7. An investigator determines the correlation coefficient between triglyceride levels and degree of atherosclerosis in sampled blood vessels to be +1.67. On the basis of this you would conclude that:

a. Triglyceride level is a good predictor of atherosclerosis

b. Triglyceride level is not a good predictor of atherosclerosis

c. High triglyceride levels cause atherosclerosis

d. Atherosclerosis cause high triglyceride levels

e. The investigator has incorrectly determined the correlation coefficient

8. A screening test of known sensitivity and specificity is applied to two populations. The prevalence of the disease being screened for is 10% in population A and is 1% in population B. Which of the following is true?

a. The percent of all negative tests that have false-negative results is lower in population A than in population B.

b. Specificity is lower in population A than in population B.

c. Reliability is higher in population A than in population B.

d. The percent of all positive tests that have false-positive results is lower in population A than in population B.

e. Specificity is higher in population A than in population B.

9. Serum cholesterol levels are obtained for four healthy men. The probability that all will fall below the 10th percentile of the distribution of cholesterol for healthy males is:

a. 0.4

b. 1 â (0.1)4

c. (0.1)4

d. (0.9)4

e. Cannot be determined from these data

10. In a diabetes screening program, the screening level for a positive blood sugar level in test 1 is set at 160 mg/dl, and in test 2 at 130 mg/dl. The sensitivity is:

a. Greater in test 1

b. Greater in test 2

c. Equal in test 1 and 2

d. Dependent on the size of the population being evaluated

BIOL 202 Lecture Notes - Lecture 1: Statistic, Standard Deviation

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