Melissa Vigdor
Melissa Paul
Jessica Beardsley
Quiz 2
[Instructions: Please be comprehensive yet concise in your answers. Use bulleted lists where
feasible rather than full sentences. You are encouraged to be creative. Please use this form to
type your responses, which can be as long or as short as you deem necessary. Include the last
names of each member of the group in the filename you send to me. The Quiz is due to me by no
later than NOON, SUNDAY OCTOBER 20TH.]
[FINAL SCORE: 87/100]
Background: You are submitting a research proposal and as part of this proposal you are
required to describe the purpose of the study, the methods you propose to use in the study, the
study hypotheses, and the statistical analyses you will use to disprove your null hypotheses.
You wish to find out if increasing daily UV exposure via sunlamps is more effective than daily
consumption of 2000 IU Vitamin D in reducing illness and injury frequency in professional
basketball players who play and practice year-round. The total study will take place over the
course of 1 year. The first 6 months is to observe illness and injury frequency. The second 6
months will be used to assess the intervention.
1. Describe the main aims of this study, and what you believe the outcomes will be (i.e., your
hypotheses).
Objective: To determine if daily UV exposure (from sunlamps) is more effective at reducing
illness and injury than daily consumption of 2000 IU of Vitamin D supplements in NBA players.
Hypothesis: Additional daily UV exposure (from sunlamps) is associated with a greater
reduction in illness and injury compared to daily consumption of 2000 IU of supplemental
Vitamin D in NBA players.
Null Hypothesis: Additional daily UV exposure (from sunlamps) is not associated with a greater
reduction in illness and injury compared to daily consumption of 2000 IU of supplemental
Vitamin D in NBA players.
2. Describe the research design you will use and explain how this design controls for internal
and external validity. Include the N for this study, and how you will create (select) each cohort
(control group, intervention, longitudinal, etc…whatever you think works best) and the n for each
cohort.
Research Design:
● Randomized Control Trial
● Experimental, longitudinal study
● N =150 (n=50 per group), male participants will be recruited from the National Basketball
Association (NBA) across the US. Ethnicity composition of sample population should
mirror that of NBA teams in US.
○ All play-eligible NBA players will receive invitation to participate
○ Volunteers will be stratified by ethnicity before being randomly assigned to one of
three treatment groups by random number generation. This will allow us to
equally represent differential processing of UV rays to create vitamin D (via the
skin)
○ Exclusion criteria: ineligible to play in NBA, current injury/illness, chronic illness
that affects vitamin D absorption (Celiac’s disease, crohn's disease), currently
taking vitamin D supplementation, female WNBA players
● 3 Treatment Groups:
○ 1. Daily UV exposure from sunlamps, 30 minutes/day
○ 2. 2000 IU of Vitamin D
○ 3. Control (no treatment)
● Intent to treat protocol
● Assessments will be taken at six designated locations depending on NBA team division:
Atlantic will be in Philadelphia, PA, Central will be in Detroit, MI, Northwest will be in
Portland, OR, Pacific will be Los Angeles, CA and the Southwest will be in Dallas, TX
● Assess serum Vitamin D (25-(OH) cholecalciferol status at 0, 3 and 6 months to
determine baseline values; continue to assess after treatment at 9 and 12 months
● Tabulate injuries and illness using a self-reported, validated questionnaire (at 0, 3, 6, 9
and 12 months)
● Collect bone mineral density (BMD) and body composition data using DEXA at 0, 6 and
12 months
● Collect activity log (average minutes and intensity per week at 0, 3, 6, 9 and 12 months)
● Collect diet log for subjects to quantify vitamin D-containing food using a food frequency
questionnaire (at 0, 3, 6, 9, and 12 months)
● Use questionnaire to assess time spent outdoors and quantify sunscreen use (at 0, 3, 6,
9, and 12 months)
● Require participants to cease using tanning beds for the duration of the 12 month study
● No other treatment group, other than sunlamp group, may use sunlamps during the
length of the study; sunlamp treatment group may not extend beyond 30 minutes/day
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No other treatment group, other than Vitamin D group, may consume vitamin D
supplements during the study; vitamin D treatment group may should not exceed 2000
IU daily supplement.
Internal Validity:
● Selection bias - We are using random selection which will increase the ability to
generalize results back to the population of male professional basketball players
● Selection-Maturation Interaction - Does not apply since our study is not a quasiexperimental design
● Instrumentation - We will use standardized protocols for blood sampling and validated
questionnaires for data collection; all assessments will take place at one of six
designated centers; all centers will use standard protocol and properly calibrated DEXA
equipment.
● History - We cannot fully control for outside factors that may contribute to injury or illness
other than vitamin D; however, we are collecting data on diet history, time outdoors and
playing time
● Maturation - Increased playing time may affect bone growth; to control for this factor, we
are gathering data on playing time
● Repeated Testing - Participants will not get feedback on their tests.; questionnaires will
collect data on any change their lifestyle during the research project
● Mortality - Intent to treat protocol
● Experimenter bias - players and researchers will be aware of the treatment they are
receiving, therefore, there is possibility for bias
● Diffusion/Crossover- We are controlling for crossover by requiring participants to NOT
use sunlamps or take Vitamin D supplements during the year of the study
External Validity:
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External validity is the ability to generalize results of a study to a population; our study is
representative of all male, professional basketball players
Large sample size (N=150) and randomization will help to avoid selection bias
Multiple-treatment interference and interaction of treatment and setting: Cannot control
sunlight players are exposed to outside of experiment; however, data collection at 0, 3, 6,
9, 12 months to account for seasonal variation from sunlight exposure
Reactive or Interactive Effect of Testing: this is not a threat to our study, only one
treatment period will be used
3. Describe the variables for this study, and identify the independent variables and the
dependent variables. Distinguish between variables that are directly obtained from the subjects
and variables that are ‘created’ from the collected variables in SPSS. If created, indicate the
formula/procedure you would use to create the variable(s).
Independent variables:
● Ethnicity
● UV sunlamp exposure (minutes/day)
● Vitamin D supplementation (IU/day)
● Age (y)
● Height (m)
● Weight (kg)
● BMI (calculated)
● Amount of vitamin D in diet (IU/day)
● Training (minutes/day)
● Outdoor sun exposure (minutes/day)
● Position of play
● Playing time (minutes/game) - (G1_Time, G2_Time, G3_Time, etc.)
● Total playing time (sum of “Playing time” minutes/game)
Dependent variables:
● Injury (# occurrences)
● Illness (# occurrences)
● Injury severity (pain scale, 1-7)
● Illness severity (severity scale, 1-7)
● Vitamin D status (serum 25-(OH) cholecalciferol, ng/ml)
● Bone mineral density (kg/m3)
● Body Fat Percentage (%)
● Lean Body Mass Percentage (%)
All variable data will be collected directly from subjects with the exception of BMI and Total
Playing Time
● To add BMI as a variable we will “insert a variable” titled “BMI” within the variable
screen of the SPSS database; under “Transform” we will select for BMI to “Compute” by
instructing “weight” variables be divided by “height” squared:
BMI = kg/m(2)
● Total Playing Time will be an inserted variable in SPSS “Ttl_Play”; under “Transform” we
will select to sum G1_Time, G2_Time, G3_Time, etc.:
● Ttl_Play = sum(G1_Time, G2_Time, G3_Time)
4. Indicate the statistical procedures you would use to (a.) describe the data collected and (b.)
disprove the null hypothesis. Make certain you describe how you will treat different genders,
ages, or other subgroups (inclusion and exclusion criteria should be clear in your responses to
A. and B. above). If you are assessing subgroups, indicate the statistical procedures you would
follow.
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Intent-to-Treat protocol - all data will be included in analysis (none excluded)
Using SPSS, run descriptive statistics
○ Frequencies for categorical variables (ex: position)
○ Central Tendencies: mean, median and mode of number of illnesses/injuries per
group
○ Histograms for continuous variables (ex: Vitamin D from diet, minutes played per
game for season)
Determine whether data is normally distributed or skewed
○ If skewed, calculate z-scores for further analysis
Use parametrics test for normally distributed data (ANOVA) / nonparametric test
(Kruskal Wallis) for skewed distribution
Conduct ANOVA to determine differences between the three treatment groups (control,
sunlamp, and Vitamin D supplementation)
Conduct repeated ANOVAs to determine how players’ illness/injury frequency change
over the year
Set statistical significance for probability at p<0.05 (confidence interval)
Analyze ethnic subgroups in comparison to the whole group to determine differences
Stratify groups by age to analyze illness/injury by quartiles to determine if age was a
factor
Control for age, activity, sunlight exposure, dietary Vitamin D in multiple regression
analysis to determine if sunlamp exposure or supplemental Vitamin D was responsible
for any differences in illness and injury
Fail to reject null hypothesis if the ANOVA finds no significant difference in the sunlamp
group in reducing illness/injury compared to supplemental Vitamin D, (p>0.05):
○ “Additional daily UV exposure (from sunlamps) is not associated with a greater
reduction in illness and injury compared to daily consumption of 2000 IU of
Vitamin D in professional basketball players”