HPHY212 - Practice Quizzes (From Graphs to Correlations + MORE!)

The plot below represents the normal distribution of resting heart rate for 100 marathon runners and 100 sprinters. What is the approximate standard deviation for both groups?

Marathoners = 2 bpm Sprinters = 5 bpm

The plot below represents the normal distribution of resting heart rate for 100 marathon runners and 100 sprinters. Calculate the 95% confidence interval for both Marathoners and Sprinters.

Marathoners. SEM = SD/sort(n) = 2/10 = 0.2. 95% Confidence interval 59.6 to 60.4 bpm Sprinters. SEM = SD/sort(n) = 5/10 = 0.5. 95% Confidence interval 69 to 71 bpm

Choose the best set of options below to fill in the following: power is needed to detect differences.

More; small

For women younger than 40 years, where there is only a moderate risk of breast cancer, there have been no randomized controlled studies done to suggest a benefit to mammogram screening. You decide to conduct an experiment to determine the accuracy of this assessment by measuring the blood pressure of 800 women, between the ages of 30 and 40. At the same time, you perform a biopsy to determine whether they really have cancer. Here are the results: What is the prevalence of cancer in this population? Does this make sense?

Prevalence = (70+30) / (70 + 30 + 280 + 420) = 12.5% Yes, low prevalence, since there is a moderate risk in this population.

Before making it available for the entire population, a group of researchers designed an experiment to evaluate the effectiveness of a new drug developed to help people relax - G23 Paxilon Hydrochlorate (Pax). The researchers believed that this drug would have the same effectiveness (reduction in heart rate), but have fewer side effects (violent incidences) than a popular drug on the market - Ritalin. Thirty subjects were randomly assigned to three groups: Pax, Ritalin and Placebo (sugar pill). Subjects were tested before treatment and then after they had been on the treatment for 6 weeks. There were no differences found between the groups for the baseline data. The alpha value was set at 0.05 for this study. Given a p-value of 0.01, what type of error should the researched be concerned about?

type I due to a false positive

An investigator examined the effect of exercise on resting heart rate by examining two randomly selected groups - one that exercised three times per week and one that did not exercise at all. After 10 weeks, the exercise group's mean resting heart rate was lower than the control group. The alpha level was set at 0.05. However, if the p-value was 0.20, what type of error shoulder the investigator be concerned about:

type II due to a false negative

Adopted from Hemming, 2019. Low back pain is highly complex with a multitude of physical, cognitive and lifestyle factors contributing to the disorder. Trunk muscle dysfunction is often regarded as a key feature of low back pain, despite being poorly understood and variable with increases, decreases and no change in muscle activity reported in the literature. In this study, 50 subjects with low back pain were recruited, along with 50 controls subjects, matched on the basis of sex, age and activity levels. Subjects were asked to bend their trunk forward as far as possible, and muscle activity of their back muscles and range of motion was measured. While the range of motion was similar between the two groups, the mean muscle activity was found to be 10% higher in the low back pain group (p=0.3). The authors conclude that higher levels of muscle activity are a risk factor for low back pain.For the p-values reported, what would be the most appropriate statistical test?

unpaired t-test

Adopted from Ottenhigm et al., 2005. Chronic obstructive pulmonary disease (COPD) has been predicted to become the third leading cause of death and the fifth most common cause of disability in the world by 2020. Weakness of the diaphragm (an inspiratory muscle) is the most important cause of death in COPD. Researchers are trying to understand the mechanism explaining this weakness. Muscle fibers were isolated from muscle biopsies from the diaphragm of nine patients with mild to moderate COPD and five patients without COPD. The researchers measured maximum force per cross sectional area, myosin heavy chain content and fraction of strongly-attached cross-bridges, with black boxes represent patients with COPD and white boxes represent patients without COPD(* p < 0.05). For the patients with COPD, the mean of their maximum force per cross sectional area (in mN*mm-2) is 200 and the standard deviation is 9. What is the 95% confidence interval for this measurement?

(194, 206)

From a sample of Human Physiology students (n=16), the mean resting heart rate was 68 bpm with a standard deviation of 12 bpm. Assuming a normal distribution, use the empirical rule to calculate the following.What is the 95% confidence interval for the average heart rate of all students in Human Physiology?

(62, 74)

An investigator examined the effect of exercise on resting heart rate by examining two randomly selected groups - one that exercised three times per week and one that did not exercise at all. After 10 weeks, the exercise group's mean resting heart rate was lower than the control group. The alpha level was set at 0.05. For which p-value would increasing the number of subjects help reduce the risk of making an error?

0.20 NOT 0.01

For the following set of numbers, what is the median: 1, 2, 3, 10, 30, 30, 36

10

For a group of normally distributed scores with a mean of 200 and a standard deviation of 10, the middle 99% of the data are between what values? The reliability coefficient for a 99% confidence interval is 2.576.

170 and 230

The height of 25 subjects was collected. The data were normally distributed, with a mean of 175 cm and a standard deviation of 5 cm. The 95% confidence intervals are between:

173 and 177 cm

The Lachman test is used to determine if a patient has a ruptured anterior cruciate ligament (ACL) in the knee. The examiner places one hand one the tibia and the other on the thigh. The tibia is then pulled anterior until the clinician feels a firm endpoint. If the amount of motion is 10 mm or greater, it is considered a positive test for an ACL tear. You decide to conduct an experiment to determine the accuracy of this assessment by comparison with an MRI, which is considered the gold standard. Here are the results: What is the prevalence of ACL tears in this population?

25%

Determined to beat your friends in your March Madness bracket pool, you design a mathematical model that predicts whether an underdog is going to upset the favorite in each matchup using the team's season statistics. You fill out your bracket based on the results of this model's prediction. For each game, your model will either predict that the underdog will win (test positive), or that the underdog will lose (test negative). After the game is complete, you then know whether the underdog actually won (condition positive), or if the underdog actually lost (condition negative). The results are below: Prediction - Underdog will win; Result - Underdog wins: 16 games Prediction - Underdog will win; Result - Underdog loses: 8 games Prediction - Underdog will lose; Result - Underdog wins: 8 games Prediction - Underdog will lose; Result - Underdog loses: 32 games What is the specificity of the test?

32/40 = 80%

Researchers examined the effects of loaded, resistance wheel running on rat muscle growth. For 8 weeks, one group of rats (n=10) had access to a resisted running wheel, another group (n=10) had access to a free spinning unloaded running wheel, and a control group (n=10) did no running. At the end of the study, researchers measured leg muscle mass and compared it to the average distance run by the rats. The correlations for both running groups is plotted in the figure. Each dot represents an individual animal. One of the animals was forgotten in measuring the muscle mass. You know it ran on an unloaded wheel and ran 3 km/day. About how much would you predict that rat's muscles to weigh?

325 mg

A researcher collects data on 75 athletes and runs a correlation analysis between quadriceps muscle mass and speed in the 100 meter dash. They find an r value of -0.60. This means that the variability in muscle mass accounts for what percentage of the variability in speed?

36%

An investigator examined the effect of running on resting heart rate (RHR) by examining two randomly selected groups - one that ran three times per week for 30 minutes, and one that did not exercise at all. The mean resting heart rate of the exercise group was 52 beats per minute (bpm), with a standard deviation of 7 bpm. There were 49 subjects in the exercise group. 95% of subjects fell within what resting heart rate range?

38-66 bpm

What is the mean score for the following set of numbers? (1, 1, 2, 3, 4, 6, 11)

4

Imagine that researchers have developed a new diagnostic blood test to identify pancreatic cancer. The test measures blood levels of a protein which is produced and released by the cancerous cells. The test yields a positive result if the protein is higher than 30 mg/dl. They test this new screening tool on 140 patients and 40 are later identified to actually have cancer. What is the specificity of this new measurement?

40%

From a sample of 16 students in our class, the mean resting heart rate was 68 bpm with a standard deviation of 12 bpm. Assuming a normal distribution, use the empirical rule to calculate the following. What percentage of students have a resting heart rate higher than 68 bpm?

50%

A physical therapist records the hip flexion range of motion in 25 patients with hip osteoarthritis. After confirming that the data are normally distributed, she reports a mean of 70 degrees with a standard deviation of 5 degrees. Which range represents 95% of the data for this population?

60 to 80 degrees

Imagine that researchers have developed a new diagnostic blood test to identify pancreatic cancer. The test measures blood levels of a protein which is produced and released by the cancerous cells. The test yields a positive result if the protein is higher than 30 mg/dl. They test this new screening tool on 140 patients and 40 are later identified to actually have cancer. What is the sensitivity of this new measurement?

75%

Researchers measure the heart rate from 100 students after taking a Human Physiology exam, and find a mean of 120 beats per minute (bpm), with a standard deviation of 20 bpm. Assuming a normal distribution, the middle 95% of the scores will be between:

80 and 160 bpm

Researchers are looking at the effects of exercise on the strength of the biceps brachii. Fifteen subjects are randomly divided into 3 groups: no exercise, low dose (3x per week for 3 weeks) and high dose (6x per week for 6 weeks).What would be the most appropriate statistical test for this study for comparing between groups?

ANOVA

What is the prevalence of ACL tears in this population?The Berg Balance Test (BBT) is primarily used to asses balance in an elderly population. Subjects are assigned a score ranging from 0 (severely impaired balance) to 56 (excellent balance). You set the cutoff of 30 for distinguishing between fallers and non-fallers (< 30 is a positive test). In order to validate this test, you administer it to 75 older adults. At the same time, you assess whether or not they have had recent episodes of falling and you classify them into 2 groups - fallers and non-fallers. Here are the results: The prevalence of this condition is 33%. Given the same sensitivity and specificity levels, what would happen to the positive predictive value if the prevalence dropped to 0.33%?

Decrease

Adopted from DeVita et al., 2016. Obesity is a primary risk factor for numerous pathologies including knee osteoarthritis (OA) and is thought to stem at least partially from obese compared with lean individuals having larger knee joint forces during gait. Researchers studied the effects of weight loss in obese subjects who underwent gastric bypass surgery. These results were compared to lean individuals, who had not undergone any surgery. Muscle forces for the hamstring and quadriceps were assessed for both groups under three conditions: baseline, 6 months post surgery and 12 months post surgery.What is the most appropriate statistical test for both of the independent variables? Justify your answer.

Group - unpaired t-test Time - repeated measures ANOVA

When using an ANOVA to compare means, a _______I______ is compared to a _____II_______.

I = F-statistic, II = F-critical value

Researchers at the UO conducted a study on the conservative management of hip osteoarthritis (OA) - "conservative" meaning no surgery. Since the majority of patients with hip OA are women, only females were included in the study. Subjects with a diagnosis of hip OA were divided into three groups based on their choice of pharmaceutical treatment - a) no drugs, b) use of the supplements Glucosamine and Chondroitin Sulfate, and c) use of pain management COX-2 inhibitors (such as Celebrex). There were 25 subjects in each group. Subjects were evaluated initially, after 1 month, 6 months and 12 months. At each evaluation, the following measurements were made on the affected hip: range of motion, pain (visual analog scale), strength, and cartilage thickness (with an x-ray). What type of statistical test would you use to compare every dependent variable between the 3 groups at only the baseline time point?

MANOVA

HOW TO SOLVE FOR 95% CONFIDENCE INTERVAL GIVEN (n), mean, and SD

SD / sqrt(n) n = sample size, not mean HAHA Mean +/- 2 CI

Prostate cancer is second only to no melanoma skin cancer and lung cancer as the leading cause of cancer and cancer death, respectively, in men. The survival rate is related to many factors, especially the time of diagnosis. Thus, a screening program that could accurately identify asymptomatic men might be expected to substantially reduce prostate cancer morbidity and mortality. A recent clinical trial of prostate-specific antigens as a screening procedure was performed. 1000 men were tested with this antigen, with a trans rectal needle biopsy serving as a gold standard. Here are the results: What is the sensitivity of this measurement?

Sensitivity = TP / (TP + FN) = 90 / (90+10) = 90%

Adopted from DeVita et al., 2016. Obesity is a primary risk factor for numerous pathologies including knee osteoarthritis (OA) and is thought to stem at least partially from obese compared with lean individuals having larger knee joint forces during gait. Researchers studied the effects of weight loss in obese subjects who underwent gastric bypass surgery. These results were compared to lean individuals, who had not undergone any surgery. Muscle forces for the hamstring and quadriceps were assessed for both groups under three conditions: baseline, 6 months post surgery and 12 months post surgery.Assume that the result of your first statistical analysis above results in a p-value of 0.01 and the for the second, the p-value is 0.30. What conclusions would you draw?

Significant difference between obese and lean groups Surgery has no effect on muscle forces NOTE - this could be reversed

Before making it available for the entire population, a group of researchers designed an experiment to evaluate the effectiveness of a new drug developed to help people relax - G23 Paxilon Hydrochlorate (Pax). The researchers believed that this drug would have the same effectiveness (reduction in heart rate), but have fewer side effects (violent incidences) than a popular drug on the market - Ritalin. Thirty subjects were randomly assigned to three groups: Pax, Ritalin and Placebo (sugar pill). Subjects were tested before treatment and then after they had been on the treatment for 6 weeks. There were no differences found between the groups for the baseline data. The alpha value was set at 0.05 for this study. The mean number of side effects was larger after the 6 week treatment when compared to baseline (the analysis resulted in a p-value of 0.3). What are the possible options?

There are no significant increases in side effects from Pax or not enough power to detect a difference

Although exercise during pregnancy is generally recommended and thought to be beneficial to both mother and fetus, the nature of the adaptations to exercise during pregnancy and why exercise may be beneficial remains poorly understood. Recent studies suggest that exercise may stimulate the expression of several pro-antigenic (blood vessel promoting) molecules, such as heat shock proteins. Researchers decided to perform a study on rats. Half of the rats were randomly assigned to exercise for 6 weeks before and during pregnancy and the other half did not exercise. On day 19 of pregnancy, tissue samples were collected from the placenta of the mother to measure heat shock proteins. The data are presented below, with the * indicating a significant difference between groups.

There is no difference in heat shock proteins between the exercise and non-exercise group

Adopted from Whedon, 2005Before making it available for the entire population, a group of researchers designed an experiment to evaluate the effectiveness of a new drug developed to help people relax - G23 Paxilon Hydrochlorate (Pax). Fifty subjects (ages 30-50) who worked in a high stress environment (college professors) were recruited and randomly assigned to two groups (Pax or no Pax). Subjects were spent 8 hours per day in a simulated work environment, where the air was pumped in with a gas containing Pax, or an inert gas, with the same smell as Pax. Measurements of heart rate and the Perceived Stress Scale (score of 0-40) were measured before treatment and then after they had been in the experiment for 1 week. Since the researchers were also interested in side effects, they measured the number of daily violent reactions of each subject (both before and after the experiment). The alpha level was set at 0.05 for this study. There were no significant differences between groups for all variables at baseline. What is the most appropriate statistical test to compare the heart rate between groups after the treatment? Justify your answer.

Unpaired t-test. Comparison between two independent groups.

Confidence intervals represent:

a way of comparing the sample mean to the population mean

Two researchers are comparing the resting blood pressure of healthy subjects and patients with diabetes. Experiment 1 is conducted in Japan and experiment 2 is conducted in the United States. In both experiments, 10 patients and 10 healthy subjects are tested. The results are presented below. What could account for different results from the two studies? random variability experimental error regional variations in the sample all of the above

all of the above

When reporting the mean and standard deviation of a population, a researcher is assuming that the...

data are normally distributed

An increase in the variability of a data set will serve to:

decrease power

A study finds that patients with higher levels of depression drink more than those with lower levels of depression. What is a reasonable conclusion for this study?

drinking is correlated with depression

Two researchers are comparing the resting blood pressure of healthy subjects and patients with diabetes. Experiment 1 is conducted in Japan and experiment 2 is conducted in the United States. In both experiments, 10 patients and 10 healthy subjects are tested. The results are presented below.

experiment 1

Before making it available for the entire population, a group of researchers designed an experiment to evaluate the effectiveness of a new drug developed to help people relax - G23 Paxilon Hydrochlorate (Pax). The researchers hypothesize that this drug would have the same effectiveness (reduction in heart rate), but have fewer side effects (violent incidences) than a popular drug on the market - Ritalin. Thirty subjects were randomly assigned to three groups: Pax, Ritalin and Placebo (sugar pill). Subjects were tested before treatment and then after they had been on the treatment for 6 weeks. There were no differences found between the groups for the baseline data.What would be the most appropriate test to compare the heart rate between groups after the treatment?

factorial ANOVA

The median survival for advanced pancreatic cancer is 4 months. This means that after diagnosis:

half of the patients will die within 4 months

The purpose of a t-test is to evaluate a:

hypothesis

A correlation of 0.0 between two variables indicates

independence (no association) between the variables

Which measure of central tendency can you use to describe nominal data

mode

What happens to the confidence in a sample mean as the sample size (n) increases?

more confident

A researcher performs a simple regression analysis and finds that variations in age can predict 50% of the variation in maximum heart rate. By adding sex as another predictor value, the researcher hopes to be able to predict

more of the variation in maximum heart rate

The plot below represents the distribution of height for men and women from 200 subjects. Is there a statistically significant difference in height between men and women?

need more information to determine

Researchers are looking at the effects of exercise on the strength of the biceps brachii. Fifteen subjects are randomly divided into 3 groups: no exercise, low dose (3x per week for 3 weeks) and high dose (6x per week for 6 weeks).The statistical analysis yields a p value of 0.15. What should the researchers be concerned about?

not enough power

A multiple regression analysis involves:

one dependent variable and multiple independent variables

What type of distribution is displayed here?

positive skew

An investigator examined the effect of running on resting heart rate (RHR) by examining two randomly selected groups - one that ran three times per week for 30 minutes, and one that did not exercise at all. You also recorded the age of each subject, and are interested in seeing if there is correlation between age and RHR. For this correlation, r = -0.45, and r2 = .20. What does each value mean? Be sure to use the words strength, direction, and variance in your answer.

r-value: represents the strength and direction of the relationship, there is a moderate, negative correlation between variables r-squared value: 20% of the variance in age accounts for the variance in RHR

The coefficient of determination is:

r2

The plot below represents the distribution of height for men and women from 200 subjects. After careful examination it was discovered that there was a problem with the experimental collection and data from half of the men needed to be thrown out. How would this affect the confidence intervals for the mean for this group? You can assume that the mean and standard deviation do not change.

range of confidence intervals would increase

Adopted from Ely et al., 2017. Histamine is a chemical that your immune system produces in response to allergens (like pollen). Histamine also contributes to elevations in skeletal muscle blood flow following exercise, which raises the possibility that histamine is an important mediator of the inflammatory response to exercise. For this study, 24 subjects were randomly assigned to one of two groups. One group took an antihistamine, Allegra, with water (blockade group) and one group just took water (control group). Measurements of inflammation, quadriceps muscle strength, and quadriceps muscle damage were obtained before and at 0, 6, 12, 24, 48, and 72 hours post exercise. Exercise consisted of downhill running for 45 minutes. Some of the results from this study are presented below (p-values represent results of comparisons between control and blockade) The fact that the researchers are testing 24 subjects is referred to as:

sampling

Although exercise during pregnancy is generally recommended and thought to be beneficial to both mother and fetus, the nature of the adaptations to exercise during pregnancy and how they may be beneficial remain poorly understood. Recent studies suggest that exercise may stimulate expression of several pro-antigenic (blood vessel promoting) molecules, such as heat shock proteins. Researchers decided to perform a study on pregnant rats. Half of the rats in this study exercised for 6 weeks before and during pregnancy and the other half did not exercise. On day 19 of pregnancy, tissue samples were collected from the placenta of the mother for analysis. The data are shown below. What does the asterisks (*) in the figure represent?

statistically significant difference between the two groups

Before making it available for the entire population, a group of researchers designed an experiment to evaluate the effectiveness of a new drug developed to help people relax - G23 Paxilon Hydrochlorate (Pax). The researchers hypothesize that this drug would have the same effectiveness (reduction in heart rate), but have fewer side effects (violent incidences) than a popular drug on the market - Ritalin. Thirty subjects were randomly assigned to three groups: Pax, Ritalin and Placebo (sugar pill). Subjects were tested before treatment and then after they had been on the treatment for 6 weeks. There were no differences found between the groups for the baseline data.With respect to heart rate, their hypothesis tested during statistical analysis is:

the null hypothesis

One hundred high school students were tested (half had suffered a concussion, half had not). The main goal of the study was to better understand the difficulties in locomotion due to concussion. Balance control was measured during gait. Subjects with a concussion were tested within 2 days of suffering a concussion (baseline) and 1 month later. Subjects without a concussion were also tested on 2 days, with a similar time between days. For the statistical test in the previous question, the researchers found a difference with a p value of 0.3. What would be a reasonable conclusion?

the research hypothesis was not supported

A patient is told that she has gout and in reality she does have gout. This is an example of a:

true positive

An investigator examined the effect of exercise on resting heart rate by examining two randomly selected groups - one that exercised three times per week and one that did not exercise at all. After 10 weeks, the exercise group's mean resting heart rate was lower than the control group. The alpha level was set at 0.05. Given a p-value of 0.01, what type of error shoulder the investigator be concerned about:

type I due to a false positive