# Pressure of the Human Circulatory System: Is Gender a Factor?

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## Abstract

Do males and females have the same systolic and diastolic blood pressure?

## Introduction

Blood pressure or arterial pressure determines the force exerted on the arteries as blood is distributed throughout the body. Blood pressure does not stay constant throughout the day or throughout one's life and changes with accordance to an individual's daily activities, eating habits, medical health, and emotional condition. An average blood pressure reading is 120/80 mmHg and is read 120 over 80. The systolic pressure of 120 symbolizes the maximum pressure exerted on the arteries when the heart beats and the diastolic blood pressure of 80 symbolizes the pressure in the arteries when the heart is at rest.

## Procedure

In this observational study I measured the blood pressure of 20 randomly selected males (ages 16-18) and 23 randomly selected females (ages 16-18). To randomize the results and have students of all different sizes and health conditions we performed a random assignment of students chosen for the study. Each student was assigned a number according to their row and seat number. For example, the first person sitting in the first row was assigned the number one. Then as I moved down the row the next person was assigned the number two and so on. I then took a random number table and chose every other number that showed up. After determining the subjects we placed an electric wrist sphygmomanometer on their wrist and measured both the systolic and diastolic blood pressure. All of the subjects were tested in the same time period during the day and were not under any stressful or physical activities. I especially made sure to ask whether or not the participant was under any stress and only tested those that were not. Furthermore, all of the subjects were of the same age group eliminating any possibility of outliers and extreme skewness in our data. For original data refer to Appendix A.

## Analysis

### Part 1

The diastolic blood pressure of females is normally distributed and almost perfectly symmetric. The range is 26 and the distribution is centered at about 71. there are no outliers in the distribution.

The diastolic blood pressure of males ranges wider than that of females and the distribution is normal with slight leftward skewness. There are no outliers and the distribution is centered at around 72, almost the equivalent of the value around which the distribution if diastolic blood pressure in females is centered.

The systolic blood pressure of males has a normal distribution with a range far greater than that of the females' distribution. The center is about 110, the value of the third quartile in the previous distribution. The interquartile range is wider as well and the distribution is more symmetric, also however with slight skewness to the right. There are no outliers.

The systolic blood pressure of females is normally distributed and slightly skewed to the right. There are no outliers present since there are no far reaching values. The center of the distribution is approximately at 99 and the range is wide, from 92-119. 50% of values are from 93 and 110, almost half of the numbers in the range.

Notice how both of the distributions of male blood pressures have wider ranges that those of females. Since blood pressure results of nutrition and level of activity as well as heredity, one can assume from the observations that the eating and exercising habits of males are more diverse than those of females. Histograms of all distributions are located below.

### Part 2

To compare the blood pressure for males and females I used a Two-Sample T-test because there were only 43 participants in this observational study. I compared the systolic and diastolic data separately.

#### Systolic Blood Pressure

Null Hypothesis (H_{0}): The mean systolic blood pressure of females is the same as that of males.

Alternative Hypothesis (H_{A}): The mean systolic blood pressure of females is not the same as that of males.

#### Conditions

A simple random sample of males and females was taken.

10% condition: 10(23) < Total population of female students.

10(20) < Total population of male students.

Normal condition: Each box plot for males and females is relatively symmetrical with no outliers. Refer to Appendix B Part 1

#### Test Statistics

t = (101.783 - 108.95)/((8.607^{2}/23) + (10.470^{2}/20) = -2.430

t = -2.430, p-value = 0.02010, df = 36.89

#### Conclusion

We have significant evidence to reject the null hypothesis because the p-value is less than 0.05. Therefore, I can conclude that the mean systolic blood pressure of males is not the same as that of females.

#### Diastolic Blood Pressure

Null Hypothesis (H_{0}): The mean diastolic blood pressure of females is the same as that of males.

Alternative Hypothesis (H_{A}): The mean diastolic blood pressure of females is not the same as that of males.

#### Conditions

A simple random sample of males and females was taken.

10% condition: 10(23) < Total population of female students.

10(20) < Total population of male students.

Normal condition: Each box plot for males and females is relatively symmetrical with no outliers.

#### Test Statistics

t = (72.087 - 72.524)/((7.128^{2}/23) + (8.376^{2}/20)) = -0.179

t = -0.179, p-value: 0.8586, df = 40.78

#### Conclusion

Since the p-value (0.8586) is so large, greater than 0.05, we have strong evidence to accept the null hypothesis. Therefore, I can conclude that the diastolic blood pressure of females is the same as that of the males.

## Overall Results

High blood pressure is the result of heredity, age, activity level, and nutrition. Males have higher blood pressure than females until the age of 55, where the risk of high blood pressure is the same for both sexes. After menopause, levels of estrogen are significantly lower, thereby increasing blood because high to medium testosterone levels are related to high blood pressure.

## Sources of Error

- People reported that they were not under any stressful conditions but they might have been.
- The wrist sphygmomanometer is known to be not as reliable as one that goes around the arm. I could have obtained more accurate results had a used a sphygmomanometer that goes around the arm.

Tatyana Nektalova -- 2005

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