HS1/OU1 2020
Assessment Title: Assignment (Part 2)
Introduction
The objective of this assignment is for you to understand research scenarios that concern analysis of variance (ANOVA). In particular, it is important that you master the different types of ANOVA, such as single factor and factorial. It is highly recommended that you attempt the assignment questions on a weekly basis where possible (after completing each module) so that the information is still fresh and does not become overwhelming if you leave it to the last minute.
Recommended timeline of assignment tasks:
- Task A | after completing module 6 & 7: Introduction to ANOVA & Multiple Comparisons
- Task B | after completing module 8: Factorial ANOVA Part I
- Task C | after completing module 9: Factorial ANOVA Part II
To successfully complete these tasks, it is highly recommended that you attend all of the lecture and tutorial sessions, and complete the accompanying activities / questions. If you have any queries, require an extension, or any other related issues, please contact the unit convenor first.
Submission:
Assignments are to be submitted via CANVAS on or before the due date. Students are expected to submit the assignments as a pdf document. The file name should be of the form Surname_Firstname_Assignment2.pdf.
SPSS Output:
Unless specifically asked for in the question, all SPSS output should be placed as an Appendix at the back of your assignment submission (see Answer Sheet).
Assessment Task
A good amount of sleep per day has the potential to predispose infants to better growth by fostering better energy self-regulation. Newborns and babies sleep differently from older children and adults. It is normal for babies to sleep in short bursts and to wake up multiple times during the night. Sleep deprived parents look for solutions to help their babies sleep longer.
Cry out – also known as the extinction method is a sleep technique that involves putting a baby to sleep by placing them in a cot and allowing them to fuss and cry until they fall asleep on their own without the parents help. The parent does not go back to the room to comfort the baby.
Controlled crying – a sleep training technique that involves putting the baby to bed and then leaving the room. If they cry the parent returns to the room after a short period of time and comforts the baby and then leave the room again.
Co-sleeping- when parents sleep in the same bed with their babies is called co-sleeping. Parents may choose to co-sleep for many reasons including cultural reasons. Experts recommend against co-sleeping because it can increase the risk of sudden unexpected death in infancy (SUDI). However there are many reasons why parents choose to co-sleep. For example many parents who sleep with their babies believe that is helps their baby feel safe and secure. Some parents co-sleep because they find it more practical.
Breastfeeding and re-settling during the night can be easier.
Consider a study in which researchers were interested in examining the amount of hours babies sleep over a 24 hours period. The study pertains to 120 babies (aged approx. 24 months). Each baby had a variety of physical and cognitive variables measured (see table below). In addition, the babies’ parents were interviewed to ascertain the sleeping method utilised when the child was between 6 months and 18 months.
- This assignment relates to the SPSS data file Assignment2.sav.
- The variables in the data file are described below:
Information on the data collected
| Variable | Variable coding | Variable description |
| ID | NA | The identification number allocated to each baby participant |
| AGE | = 6-12 months = 12-18 months | Babies age in months |
| Cultural Background [Culture] | = Western = Asian | Baby’s background / culture (as identified by the parents) |
| Sleep | Amount of sleep per 24 hrs | A measure of total amount of sleep recorded overall naps and night sleep, where higher scores represent higher amount of sleeping hours |
| Body Mass Index [BMI] | NA | A measure of total body fat based upon a baby’s height and weight |
| BMI Classification [BMI_Class] | = Underweight = Normal range = Overweight | The BMI category based upon the calculated BMI |
| Sleep training Method [Method] | = cry-out = co-sleeping = controlled crying | Sleep training method (as recalled by parent) used when the baby was between 0 and 12 months |
| Feedtype | 1=Breast Fed 2=Formula Fed 3=Mix (BF and FF) | Feeding Method |
| Age | NA | The age (measured in months) of each baby participant |
| Mother’s Work Status [MWS] | = Not working = Currently working | Whether the baby’s mother is currently working |
| Father’s Work Status [FWS] | = Not working = Currently working | Whether the baby’s father is currently working |
| Household income [INC] | NA | The combined annual work income of all household members |
| Number of Siblings [NS] | = No siblings = Has one sibling = Has two or more siblings | Whether the baby has a sibling(s) |
TASK A (16 marks)
The researchers of this study investigated potential differences in amount of sleep (recorded over 24hrs) in babies. It was hypothesised that: (1) Babies trained to co-sleep would sleep more compared to babies trained with ‘cry out’ method, and (2) babies trained with ‘cry out’ method would sleep more compared to babies trained using ‘controlled’ crying.
Using the data in the file Assignment2.sav, carry out the appropriate analyses to address these hypotheses AND write a report of your findings. For this task, use a FIGURE when reporting the descriptive statistics
Note 1: Assume all assumptions have been met
Note 2: Check the marking rubric to see how this question is graded
Note 3: See the Module 6 AND 7 content for sample reports
TASK B (18 marks)
After examining their results (from Part A) the researchers were interested in including an additional variable into their model: babies’ age (there are two categories of age 1= 6-12 months and 2=12-18 months). This new study consists of the following hypotheses: (1) babies trained to co-sleep would record more hours of sleep per day compared to babies trained using cry-out AND controlled crying method and (2) this difference in amount of sleep clocked in 24 hours is affected by babies age.
Using the data in the file Assignment2.sav, carry out the appropriate analyses to address these hypotheses AND write a report of your findings. For this task, use a TABLE when reporting the descriptive statistics
Note 1: Assume all assumptions have been met
Note 2: Check the marking rubric to see how this question is graded
Note 3: See the Module 8 AND 9 content for sample reports
TASK C (20 marks)
In a follow up study, the researchers are interested in investigating the effects of differences in body mass index [BMI] for different levels of feeding methods. Further, they would like to include baby’s cultural background as an additional factor. This new study consists of the following hypotheses: (1) Babies breast-fed (BF) would have higher BMI compared to babies fed using formula (FF) AND MIX method (BF and FF), and (2) this difference in BMI would be greater for babies from Western cultural backgrounds compared to babies from Asian cultural backgrounds.
The researchers have used the Assignment2.sav data file to address the hypotheses and wrote their own report (see next page). Unfortunately, some sections of their report contains errors. Your task is identify any errors from the six sections in this report and comment on what should have been written instead.
Note 1: Assume all assumptions have been met
Note 2: See the ANSWER SHEET document for an example of how to structure this question
Note 3: There can be multiple errors in each section
Note 4: If you agree with a particular section then just write “no errors in this section”
TASK C REPORT – as written by the researchers of this study
| Section 1: | A study was conducted to compare the body mass index (BMI) of babies across three types of feeding methods: Breast-fed (BF), Formula Fed (FF) and Mix (BF and FF). It was hypothesised that babies fed with formula would have higher BMI compared to BF babies. It was also hypothesised that this difference in BMI will be observed in babies from Asian cultural backgrounds but not Western cultural backgrounds. Figure 1 below provides a means plot for this scenario. |
| Section 2: | |
| Section 3: | A 3 (feeding method) by 2 (cultural background) Factorial ANOVA was conducted to address the aforementioned hypotheses. The main effect for Feeding Method was significant, F(2,114) = 24.97, p < .001, partial eta squared = .24. In addition, the results indicated that the interaction between Feeding Method and Cultural Background was also significant, F(2,114) = 18.09, p < .001, partial eta squared = .31. |
| Section 4: | Separate analyses were conducted for each group. For babies with Western cultural backgrounds, there was no significant mean difference for BMI across feeding method, F (2, 57) = 1.64, p = .203.* For babies with Asian cultural backgrounds, there was a significant mean difference for BMI across Feeding Method, F (2, 57) = 37.61, p < .001, eta-squared =.57. Planned contrast revealed that BMI is significantly higher for formula fed compared to breast-fed and mix methods, t (41.05) = -5.75, p < .001. |
| Section 5: | Overall, the hypotheses are partially supported. As expected, BMI is higher for babies fed with formula compared to breastfeeding method and MIX methods. Contrary to expectations, this difference was observed in Western babies only and not in Asian babies. |
| Section 6: | * A power analysis indicated that with 2, 57 degrees of freedom, there was only a 38% chance of detecting an effect of .06, and therefore we can be confident if there is an effect, it is only very small |
