# in 2010, a medical research group reported the results of an experiment to evaluate the effectiveness of acupuncture to treat a chronic intestinal condition. a group of volunteers with the chronic intestinal condition agreed to participate in the experiment and be randomly assigned to either a true acupuncture treatment or a placebo treatment. the placebo treatment mimicked the application of acupuncture, but no needle penetrated the skin. random assignment resulted in 78 subjects receiving acupuncture and 75 subjects receiving the placebo treatment. after receiving 6 treatments over the course of 3 weeks, patients were asked to report whether they had experienced a reduction in the chronic intestinal condition. the table summarizes the data from the study, with expected cell counts in parentheses.

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get in 2010, a medical research group reported the results of an experiment to evaluate the effectiveness of acupuncture to treat a chronic intestinal condition. a group of volunteers with the chronic intestinal condition agreed to participate in the experiment and be randomly assigned to either a true acupuncture treatment or a placebo treatment. the placebo treatment mimicked the application of acupuncture, but no needle penetrated the skin. random assignment resulted in 78 subjects receiving acupuncture and 75 subjects receiving the placebo treatment. after receiving 6 treatments over the course of 3 weeks, patients were asked to report whether they had experienced a reduction in the chronic intestinal condition. the table summarizes the data from the study, with expected cell counts in parentheses. from EN Bilgi.

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In 2010, a medical research group reported the results of an experiment to evaluate the effectiveness of acupuncture to treat a chronic intestinal condition. A group of volunteers with the chronic intestinal condition agreed to participate in the experiment and be randomly assigned to either a true acupuncture treatment or a placebo treatment. The placebo treatment mimicked the application of acupuncture, but no needle penetrated the skin. Random assignment resulted in 78 subjects receiving acupuncture and 75 subjects receiving the placebo treatment. After receiving 6 treatments over the course of 3 weeks, patients were asked to report whether they had experienced a reduction in the chronic intestinal condition. The table summarizes the data from the study, with expected cell counts in parentheses.

Yes No Total

Acupuncture 41 (37.2) 37 (40.8) 78

Placebo treatment 32 (35.8) 43 (39.2) 75

Total 73 80 153

Which of the following is true about the chi-square test for homogeneity?

**A)T**he number of subjects randomly assigned to each treatment is not the same; therefore, it is not appropriate to use a chi-square test for homogeneity across treatment groups.

**B)**Volunteers do not constitute a random sample from the population of all patients with the chronic intestinal condition; therefore, it is not appropriate to use a chi-square test for homogeneity across treatment groups.

**C)**Volunteers with the chronic intestinal condition were randomly assigned to each treatment, so the independence condition has been met.

**D)**Not all of the observed cell counts are large enough to satisfy the conditions for applying the chi-square test of homogeneity.

**E)**Not all of the expected cell counts are large enough to satisfy the conditions for applying the chi-square test for homogeneity.

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A veterinarian keeps track of the types of animals treated by an animal clinic. The following distribution represents the percentages of animals the clinic has historically encountered. If the animal clinic treats 230 animals in a month, how many of each animal type would be expected?

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Dogs 140.3; Cats 50.6; Livestock 18.4; Birds 13.8; Other 6.9

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A private lake sells boating memberships and currently has 600 members. During the application process the potential members are asked which recreational activity they do the most. Their choices are fishing, skiing, boarding, swimming, or tubing. The lake manager chooses clients according to their interests to maximize the use of all areas of the lake. Every month, the lake rangers randomly sample the boats on the lake and categorize them according to the activity they are doing. The lake manager performs a chi-square goodness-of-fit test using the following null hypothesis to see whether their samples differ significantly from what the original applications claim.

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46≤n≤60

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### Terms in this set (46)

A veterinarian keeps track of the types of animals treated by an animal clinic. The following distribution represents the percentages of animals the clinic has historically encountered. If the animal clinic treats 230 animals in a month, how many of each animal type would be expected?

Dogs 140.3; Cats 50.6; Livestock 18.4; Birds 13.8; Other 6.9

A private lake sells boating memberships and currently has 600 members. During the application process the potential members are asked which recreational activity they do the most. Their choices are fishing, skiing, boarding, swimming, or tubing. The lake manager chooses clients according to their interests to maximize the use of all areas of the lake. Every month, the lake rangers randomly sample the boats on the lake and categorize them according to the activity they are doing. The lake manager performs a chi-square goodness-of-fit test using the following null hypothesis to see whether their samples differ significantly from what the original applications claim.

46≤n≤60

A company claims they produce their mixed bag of candies so that, of the candies in the bag, 20 percent are dark chocolate, 60 percent are milk chocolate, and 20 percent are white chocolate. In a random sample of candies of size 50, the counts are as follows: 6 dark, 32 milk, and 12 white. Assuming the conditions for inference are met, what is the test statistic for a chi-square goodness-of-fit test to investigate whether the distribution of the sample is consistent with the company's claim?

χ2=(6−10)^2/10 + (32−30)^2/30 + (12−10)^2/10

Which of the following is an appropriate description of the chi-square distribution?

A chi-square distribution will only contain positive values and will be skewed right, with the skew becoming less pronounced with increasing degrees of freedom.

A local restaurant claims that it gets 45 percent of its customers from Monday through Thursday, 20 percent on Friday, 20 percent on Saturday, and 15 percent on Sunday. How many degrees of freedom should be used to conduct a chi-square goodness-of-fit test of the claim?

3

How are the expected counts calculated when a chi-square goodness-of-fit test is conducted?

The expected counts are calculated by multiplying each proportion in the null hypothesis by the sample size.

A fisheries biologist collected a random sample of fish from a lake and conducted a chi-square goodness-of-fit test to see if the distribution of fish changed over time. The table below shows the distribution of fish that were put into the lake when it was originally stocked. The biologist found evidence to reject the null hypothesis in favor of the alternative hypothesis. Which of the following represents the alternative hypothesis of the test?

At least one of the fish proportions is different than the corresponding proportion when the lake was originally stocked.

Which of the following is not a condition for a chi-square goodness-of-fit test?

The distribution of the sample should be approximately normal.

For which of the following is a chi-square goodness-of-fit test most appropriate?

Determining whether a categorical variable has a significantly different distribution of proportions than the expected distribution

A quality control specialist tests samples of the seed being packaged and uses a chi-square goodness-of-fit test to see whether the proportions in the samples match what is claimed by the company. Which of the following best describes the null hypothesis and the alternative hypothesis for the test?

H0: pF=0.55,pB=0.22,pBG=0.10,pI=0.07,pNG=0.06

Ha: At least one of the proportions is different.

A chi-square goodness-of-fit test where all assumptions were met yielded the test statistic χ2=12.4. Henry claims the corresponding p-value of 0.03 means that the probability of observing a test statistic of χ2=12.4 is 0.03, assuming the null hypothesis is true. Which of the following is a valid criticism of this interpretation of the p-value?

The p-value is not the probability of observing 12.4 exactly.

## Placebo and nocebo effects in randomized double blind clinical trials of agents for the treatment of fatigue in advanced cancer patients

We have previously reported significant response to placebo in randomized controlled trials of treatments for cancer related fatigue (CRF). We conducted a retrospective study to determine the frequency and predictors of response to placebo effect and ...

Cancer. Author manuscript; available in PMC 2011 Feb 1.

Published in final edited form as:

Cancer. 2010 Feb 1; 116(3): 766–774.

doi: 10.1002/cncr.24751

PMCID: PMC2815077

NIHMSID: NIHMS153279

PMID: 19918921

## Placebo and nocebo effects in randomized double blind clinical trials of agents for the treatment of fatigue in advanced cancer patients

Maxine de la Cruz, M.D., David Hui, M.D., Henrique A. Parsons, M.D., and Eduardo Bruera, M.D.

Author information Copyright and License information Disclaimer

The publisher's final edited version of this article is available free at Cancer

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## Abstract

### Background

We have previously reported significant response to placebo in randomized controlled trials of treatments for cancer related fatigue (CRF). We conducted a retrospective study to determine the frequency and predictors of response to placebo effect and nocebo effect in patients with CRF treated in those trials.

### Methods

We reviewed the records of 105 patients who received placebo in two previous randomized clinical trials conducted by our group and determined the proportion of patients who demonstrated clinical response to fatigue, defined as an increase in FACIT-F score of 7 or greater from baseline to day 8, and the proportion of patients with a nocebo effect, defined as those reporting >2 side effects. Baseline patient characteristics and symptoms recorded using the Edmonton Symptom Assessment Scale (ESAS) were analyzed to determine their association with placebo and nocebo effects.

### Results

59 (56%) patients had a placebo response. Worse baseline anxiety and well-being subscale score (univariate) and well-being (multivariate) were significantly associated with placebo response. Common side effects reported were insomnia (79%), anorexia (53%), nausea (38%) and restlessness (34%). Multivariate analysis showed that worse baseline (ESAS) sleep, appetite, and nausea were associated with increased reporting of the corresponding side effects.

### Conclusions

More than half of advanced cancer patients enrolled in CRF trials had a placebo response. Worse baseline physical well-being score was associated with placebo response. Patients experiencing specific symptoms at baseline were more likely to report these as side effects of the medication. These findings should be considered in the design of future CFR trials.

**Keywords:**fatigue, placebo, nocebo, neoplasms

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## Introduction

Cancer related fatigue (CRF) is defined as “a distressing persistent, subjective sense of tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and interferes with usual functioning and does not usually resolve with rest”.1 CRF is the most common symptom reported in patients with advanced cancer 2, 3 and is estimated to be present in about 60–90% of patients receiving active treatment, and in 30–75% of cancer survivors.4–6 Multiple therapeutic approaches have been proposed to treat this condition. To date, however, there is no single drug intervention considered standard treatment from CRF.

In two randomized controlled trials, our group investigated the psychostimulant methylphenidate and the anticholinesterase inhibitor donepezil in the treatment of CRF. These trials failed to demonstrate a significant difference between the drugs and placebo. In both trials, we noted considerable response to placebo.7, 8 This so-called placebo effect has previously been extensively described in the literature for pain, Parkinson’s disease, the immune system, asthma and depression.9–12

Placebo is described as a biologically inert substance, or any other form of therapy or intervention, that when given as an intervention is not expected to produce favorable outcomes. A placebo effect is any favorable psychobiological effect following the administration of a placebo.13 To distinguish the therapeutic effect of an inert substance from the harmful effects that it may cause, the term nocebo, which in Latin means “I will harm”, is used. A nocebo effect is defined as any distressing effect of a placebo, and is less studied in the literature.14

As with randomized controlled trials of treatments for other symptoms, such as pain, randomized controlled trials of treatment for fatigue may be influenced by significant confounding effect of the placebo effect and nocebo effect which may prevent accurate estimation of the power needed to determine efficacy. To our knowledge, no studies have been published that show the placebo and nocebo effects on fatigue. The purpose of our study was to determine the frequency and predictors of placebo and nocebo effect in patients with CRF, which could allow for better design of future fatigue treatment trials and also aid future researchers in their interpretation of results, particularly with regard to reported side effects.

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## Methods

We conducted new analyses of data already collected from 254 patients with CRF who participated in two clinical trials previously conducted by our team between July, 1st, 2003 and July 6, 2006. The current study was approved by the institutional review board of The University of Texas MD Anderson Cancer Center. Two trials have already been reported.7, 8 In one trial, patients were randomly assigned to receive either methylphenidate or placebo, and in the other trial, patients were randomly assigned to receive either donepezil or placebo. The patients took their medications for 7 days. All patients had advanced cancer and reported a fatigue score of at least 4 on the Edmonton Symptom Assessment Scale (ESAS)15 during the last 24 hours on at least 4 consecutive days. Medications, including chemotherapy that the patients were already taking prior to the trial were not restricted or discontinued. Patients taking anti-depressants were on stable doses during the study period. The patients were included in the current retrospective study if they received placebo as an intervention for fatigue. There were 22 patients randomized to placebo who were not evaluable due to dropping out or missing data. A total of 105 patients who received placebo in the two previous trials were pooled for analysis. Data collection is described in the flowchart in Figure 1.

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