Biostatistics Semester 1 Week 4 PDF

Semester 1 Week 4 BIOSTATISTICS DENT1007 BIOSTATISTICS Stem and Leaf Plots  DENT1007 BIOSTATISTICS A stem and leaf pl...

Semester 1 Week 4 BIOSTATISTICS DENT1007 BIOSTATISTICS Stem and Leaf Plots  DENT1007 BIOSTATISTICS A stem and leaf plot of Systolic blood pressure (mmHG) of 112 patients. the systolic blood pressure data 116 130 134 158 138 98 130 170 120 104 125 136 160 126 Frequency Stem Leaf 140 110 116 108 138 104 125 120 130 120 128 123 110 140 2 9. 68 96 124 110 140 120 130 145 144 140 140 145 117 120 120 138 2 10. 44 98 110 130 118 120 120 125 135 140 118 130 132 162 133 112 110 122 120 152 110 160 112 150 122 158 110 118 115 133 4 10. 5588 122 112 145 128 140 120 110 105 110 105 145 112 124 122 17 11. 00000000000022222 120 140 110 120 150 129 179 118 108 110 144 125 123 117 10 11. 5667788888 120 118 120 131 96 127 130 131 112 138 126 162 110 130 22 12. 0000000000000022223344 10 12. 5555667889 14 13. 00000000112334 6 13. 568888 10 14. 0000000044 4 14. 5555 3 15. 002 2 15. 88 0 16. 0022 The first column shows the frequency for each leaf. 1 17. 0 1 17. 9 In the stem and leaf plot, the first one or two digits form the stems and the last digits of the observed values constitute the leaves. In a sense a stem and leaf plot is an ex- tension of a histogram. An important advantage of a stem and leaf plot over a histogram is that the plot provides all the information contained in a histogram while preserving the value of the individual observations. DENT1007 BIOSTATISTICS Stem and Leaf Plots The steps for constructing a stem and leaf plot can be summarized as follows: 1.Separate each value of the measurement into a stem component and a leaf component. The stem component consists of the number formed by all but the rightmost digit of the value. For example, the stem of the value 76.8 is 76 and the leaf is 8. For the value 45.6, the stem is 45 and the leaf is 6. 2.Write the smallest stem in the data set at the top of the plot, the second smallest stem below the first stem, and so on. The largest stem is placed at the bottom of the plot. Alternatively, the largest stem can be placed at the top of the plot and the smallest stem at the bottom. 3.For each measurement in the data, find the corresponding stem and write the leaf to the right of the vertical line or period. It is convenient, although it is not necessary, to write the leaves in ascending order, that is, the smallest first and the largest at the end of the row. DENT1007 BIOSTATISTICS CLINICAL TRIALS AND DESIGNS  DENT1007 BIOSTATISTICS CLINICAL TRIALS AND DESIGNS “Clinical trial design is an important aspect of interventional trials that serves to optimize, ergonomise and economize the clinical trial conduct. The purpose of the clinical trial is assessment of efficacy, safety, or risk benefit ratio. Goal may be superiority, non-inferiority, or equivalence.” NIH (National Institute of Health, US) Investigational A treatment can be a treatment is both drug, medical device, A research study that is done to find out if a treatment can safe and effective for medical procedure, people with a or a change in a improve people’s health particular disease or person’s behavior condition. such as diet or exercise. DENT1007 BIOSTATISTICS CLINICAL TRIALS AND DESIGNS  DENT1007 BIOSTATISTICS An experimental study that involves human subjects is called a clinical trial. People who take part in clinical trials are volunteers, who can be called as “participants” or “subjects.” People participate in clinical trials, help contribute to medical research for a new or better treatment. The results of every clinical trial give researchers more information about the risks and benefits of the treatments in the trial. DENT1007 BIOSTATISTICS Experiment i A typical experiment in health sciences includes an experimental group (or treatment group), a negative control group, and a positive control group. A ne g a t ive c o nt r o l group is Negativ synonymous with most people’s idea Experimental e of a control. The Group Control subject’s response is observed (Treatment Group) Group in an untreated group or a placebo The purpose of control groups is group. to set up a direct comparison Positiv with the experimental group. e A positive control group is a treatment Control group that shows the subjects are Group capable of response.. Positive control is also known active as control. A Typical Experiment in Health Sciences  DENT1007 BIOSTATISTICS CLINICAL TRIALS AND DESIGNS Placebo is an inactive medication with the same taste, texture, etc. as the active medication but has no intended theraupetic value. It could be sterile water, saline solution, sham surgery, inert injections or even a sugar pill. A placebo makes the patient psychologically feel better. Placebo effect is hence the phenomena in which some people experience benefits after the administration of an inactive substance or sham treatment. The placebo effect can be measured by administering a placebo to participants who do not receive the test treatment (the control group) when no standard treatment exists.  DENT1007 BIOSTATISTICS CLINICAL TRIALS AND DESIGNS Example: Wellness, Inc. was about to introduce a new mouth rinse product for the prevention of gingivitis. The product was tentatively named Oral-Fresh. Oral Experimetal 70 Patients Fresh Group Amount of To assess the effectiveness Negative Control Mouth rinse Placebo 70 Patients of the mouthrinse, Group the gingival index of each Rinsing time patient was measured Peridex Positive Control 70 Patients and at the 3-month time Group point. Same Total, 210 Patients to These subjects were randomly = Control the assigned to each of the three SAMPLE SIZE Experiment treatment groups DENT1007 BIOSTATISTICS CLINICAL TRIALS AND DESIGNS The trial can be conducted as a single-blind or a double-blind. What is Single-Blind or Double-Blind study?  DENT1007 BIOSTATISTICS Single-blind study: Patients don’t know whether they are in the experimental or control group. Only the participating subjects are blinded with regard to whether they are treatment or control subjects. Double-blind study: Both patients and investigators are kept uninformed about the treatment.  DENT1007 BIOSTATISTICS CLINICAL DESIGNS: Parallel groups design: The simplest and most widely used design for clinical trials is the paral lel groups design (also called parallel design). In a parallel design, subjects are randomly assigned to receive only one of the treatments, without considering their prognostic variables. Although it is simple and easy to apply, the parallel design allows subjects to receive only one of the treatments, with the object of studying differences between the treatments. Example: Group A TreAatm peanrtaX llel stu Trdeyatm heanst Ya, ll groups receiving completely separate treatments in parallel. For example, group A receives treatment X while group B receives treatment Y. Group B Treatment Y Treatment X  DENT1007 BIOSTATISTICS Crossover design: The design in which subjects receive all of the treatments sequentially in time is known as a crossover design. Here, each subject receives two or more different treatments. Example: In this design each subject receives both treatments; half the subjects are randomly selected to receive treatment A first and then, after a suitably chosen period of time, Crossover design with 2 called “washout period”, cross over to treatments: treatment B. Washout The washout period is necessary to prevent xxxx A B the carryover effect of the first treatment Washou persisting into the time period of the second xxxx B t A treatment. The washout period must be long enough to remove the carryover effect.  DENT1007 BIOSTATISTICS Example: Crossover design with 2 treatments: Washout The main advantages of the crossover design are xxxx A B that the subjects act as their own control and that Washou the treatments are compared within subjects. xxxx B t A In a crossover design with two treatments, for example, each subject provides two measurements: 1.Treatment A The difference between these two measurements will eliminate any subject effect from the comparisons. 2.Treatment B. In fact, this is the purpose of the crossover design: to eliminate treatment effects arising from differences among the subjects. DENT1007 BIOSTATISTICS Example: For the clinical trial with three treatments, there are three groups of subjects Crossover design with 3 treatments: Washou Washou xxx A t B t C x Washou Washou xxx B t C t A x Washou Washou xxx C t A t B x DENT1007 BIOSTATISTICS EXERCISES: For the following dental variables, indicate if the measurement is qualitative or quantitative. For quantitative variables, indicate whether they are discrete or continuous. a. Patient status b. Color of gingiva c. Length of a crown d. Root resorption e. Number of amalgam fillings f. Pulse rate g. Orthognathic jaw classification h. Sensitivity of tooth i. Treatment time j. Number of patients without medical insurance k. Golf score l. Anxiety level m. Type of mucosa n. Mercury concentration in amalgam o. Size of periradicular lesion p. Shear strength of a bonding material DENT1007 BIOSTATISTICS EXERCISES: Classify measures of the following according to the level of measurement scale. a. Amount of new bone growth b. Tooth mobility c. Bone graft type d. Drilling temperature e. Soft tissue thickness f. Interfacial width g. Type of surgical approach h. Occlusal force measured in millipascals j. Type of filling material in root canal k. Degree of curvature of a root l. Level of complexity in a surgical procedure m. Type of drug used in general anesthesia n. Amount of epithelial growth o. Shape of alveolar ridge p. Number of roots obturated q. Bite force DENT1007 BIOSTATISTICS Thank you ! Dr. AYŞE SENA KABAŞ SARP BAHCESEHIR UNIVERSITY FACULTY of DENTISTRY Phone: + 90 532 441 25 60 E-mail: [email protected] DENT1007 BIOSTATISTICS DENT1007 BIOSTATISTICS Thank you ! Dr. AYŞE SENA KABAŞ SARP BAHCESEHIR UNIVERSITY FACULTY of DENTISTRY Phone: + 90 532 441 25 60 E-mail: [email protected]