EXAM 1 Mastercards Flashcards
What is the primary purpose of using statistics in analytical chemistry?
A. To eliminate variability in measurements
B. To provide tools for drawing conclusions from data
C. To ensure all measurements are the same
D. To increase the number of experimental runs
B. To provide tools for drawing conclusions from data
Statistics help chemists draw conclusions from data that inherently has variability.
What is meant by variability in experimental measurements?
A. All measurements are identical
B. Measurements differ slightly due to random or systematic factors
C. Measurements are completely unpredictable
D. Variability is eliminated by using better equipment
B. Measurements differ slightly due to random or systematic factors
Variability refers to the fact that measurements can differ due to random or systematic factors.
Which statistical tool is commonly used to estimate the precision of an analytical method?
A. Mean
B. Standard deviation
C. Median
D. Range
B. Standard deviation
Standard deviation is a measure of the dispersion or precision of data points around the mean.
What does a low standard deviation indicate in an experiment?
A. High variability in the data
B. Low variability in the data
C. The data is skewed
D. The median is higher than the mean
B. Low variability in the data
A low standard deviation indicates that the data points are close to the mean, meaning low variability.
Which of the following is NOT a source of error in experimental measurements?
A. Systematic error
B. Random error
C. Human error
D. Precise error
D. Precise error
“Precise error” is not a recognized source of error in experimental measurements.
What is a systematic error in the context of analytical chemistry?
A. Error that occurs randomly and unpredictably
B. Error that consistently skews results in one direction
C. Error that reduces variability in the data
D. Error that occurs due to random chance
B. Error that consistently skews results in one direction
A systematic error is a consistent error that skews results in a particular direction.
Which of the following statistical measures is used to describe the central tendency of data?
A. Variance
B. Standard deviation
C. Mean
D. Range
C. Mean
The mean is a measure of central tendency, summarizing the average of data points.
What is the purpose of confidence intervals in statistical analysis?
A. To estimate the likelihood of a random error
B. To provide a range in which the true value is likely to fall
C. To eliminate variability in data
D. To increase the precision of measurements
B. To provide a range in which the true value is likely to fall
Confidence intervals give a range around a sample statistic that is likely to contain the true population parameter.
What does a 95% confidence interval mean?
A. 95% of the data points are within the interval
B. There is a 95% chance that the interval contains the true value
C. 95% of experiments will have no error
D. The interval eliminates 95% of variability
B. There is a 95% chance that the interval contains the true value
A 95% confidence interval means there is a 95% probability that the interval contains the true population parameter.
Which of the following is true about random errors?
A. They can be completely eliminated
B. They affect the precision of measurements
C. They always occur in the same direction
D. They are systematic and predictable
B. They affect the precision of measurements
Random errors affect the precision of measurements but cannot be completely eliminated.
How is the accuracy of an experiment typically assessed?
A. By calculating the mean
B. By comparing the experimental results to a known true value
C. By calculating the standard deviation
D. By minimizing random error
B. By comparing the experimental results to a known true value
Accuracy is assessed by comparing the experimental results to a known or accepted true value.
What is the difference between accuracy and precision?
A. Accuracy refers to consistency, while precision refers to closeness to the true value
B. Precision refers to consistency, while accuracy refers to closeness to the true value
C. Accuracy and precision are the same concept
D. Precision can be measured, but accuracy cannot
B. Precision refers to consistency, while accuracy refers to closeness to the true value
Precision refers to the consistency of repeated measurements, while accuracy refers to how close those measurements are to the true value.
What is the purpose of a null hypothesis in statistical testing?
A. To prove that the experimental hypothesis is correct
B. To provide a statement that can be tested and possibly disproven
C. To eliminate variability in the data
D. To ensure the experiment has no errors
B. To provide a statement that can be tested and possibly disproven
The null hypothesis provides a testable statement that can be rejected or failed to be rejected based on evidence.
When the p-value is less than α (alpha), what decision is made regarding the null hypothesis?
A. Accept the null hypothesis
B. Reject the null hypothesis
C. Fail to reject the null hypothesis
D. Increase the sample size
B. Reject the null hypothesis
When the p-value is less than α, we reject the null hypothesis, indicating a statistically significant result.
Which statistical test is used to compare the means of two independent groups?
A. Paired T-test
B. One-way ANOVA
C. Independent T-test
D. Chi-square test
C. Independent T-test
The independent T-test compares the means of two independent groups.
Which of the following best describes the concept of statistical power?
A. The probability of making a Type I error
B. The ability to detect a true effect when one exists
C. The probability of the null hypothesis being true
D. The number of experimental runs required
B. The ability to detect a true effect when one exists
Statistical power refers to the likelihood of detecting a true effect when it exists, reducing the chance of a Type II error.
What does a p-value represent in hypothesis testing?
A. The probability that the null hypothesis is true
B. The probability of obtaining the observed results assuming the null hypothesis is true
C. The probability that the alternative hypothesis is true
D. The probability that a Type I error has occurred
B. The probability of obtaining the observed results assuming the null hypothesis is true
A p-value represents the probability of obtaining the observed data, or more extreme results, assuming the null hypothesis is true.
Which statistical test is used to analyze the relationship between two continuous variables?
A. Chi-square test
B. Correlation analysis
C. Independent t-test
D. One-way ANOVA
B. Correlation analysis
Correlation analysis is used to measure the strength and direction of the relationship between two continuous variables.
What is the primary difference between a population and a sample in statistics?
A. A population includes all possible observations, while a sample includes a subset
B. A sample is always larger than a population
C. A population is used for hypothesis testing, while a sample is not
D. A sample is used to calculate mean, while a population is not
A. A population includes all possible observations, while a sample includes a subset
A population includes all possible observations, while a sample is a subset of the population used for analysis.
Which of the following statements is TRUE about the mean and median in a normal distribution?
A. The mean is always greater than the median
B. The mean and median are equal
C. The median is always greater than the mean
D. The mean and median are unrelated
B. The mean and median are equal
In a normal distribution, the mean and median are equal.
What is the primary purpose of experimental design in scientific research?
A. To eliminate variability in results
B. To ensure that experiments are repeatable
C. To test hypotheses in a controlled and systematic way
D. To increase the complexity of experiments
C. To test hypotheses in a controlled and systematic way
The goal of experimental design is to test hypotheses in a controlled and systematic manner, ensuring the results are valid and interpretable.
In hypothesis testing, which of the following is considered the null hypothesis (H₀)?
A. The hypothesis that there is no effect or no difference
B. The hypothesis that there is a significant effect
C. The hypothesis that experimental results are biased
D. The hypothesis that the experiment has failed
A. The hypothesis that there is no effect or no difference
The null hypothesis is typically the assumption that there is no effect, no difference, or no relationship between variables.
What is the alternative hypothesis (H₁) in hypothesis testing?
A. There is no effect or difference
B. There is a significant effect or difference
C. The hypothesis that the experiment failed
D. The hypothesis that the test was biased
B. There is a significant effect or difference
The alternative hypothesis posits that there is a significant effect or difference between groups or conditions.
Which of the following best describes a Type I error?
A. Failing to reject a false null hypothesis
B. Rejecting a true null hypothesis
C. Accepting the alternative hypothesis when it is false
D. Failing to detect an effect when one exists
B. Rejecting a true null hypothesis
A Type I error occurs when the null hypothesis is erroneously rejected, meaning a false positive result is concluded.