Here is the design of a clinical trial:

Official Title: The Potential Impact of Aging Stereotypes in the Assessment of Memory Deficits and Screening for Prodromal State of Alzheimer's Disease

Included conditions:
- Mild Cognitive Impairment (MCI)

Study Armgroups:
- {'label': 'Standard instruction', 'type': 'ACTIVE_COMPARATOR', 'interventionNames': ['Diagnostic Test: Diagnosis of MCI versus No MCI (SCI or healthy patient)']}
- {'label': 'Reduced threat instruction', 'type': 'EXPERIMENTAL', 'interventionNames': ['Diagnostic Test: Diagnosis of MCI versus No MCI (SCI or healthy patient)']}

Interventions:
- {'type': 'DIAGNOSTIC_TEST', 'name': 'Diagnosis of MCI versus No MCI (SCI or healthy patient)', 'description': 'Neuropsychological tests', 'armGroupLabels': ['Reduced threat instruction', 'Standard instruction']}
- {'type': 'DIAGNOSTIC_TEST', 'name': 'Diagnosis of MCI versus No MCI (SCI or healthy patient)', 'description': 'Neuroimaging biomarkers of neurodegeneration', 'armGroupLabels': ['Reduced threat instruction', 'Standard instruction']}

Primary Outcomes:
- {'measure': 'Neuropsychological tests', 'description': 'Neuropsychological battery used for the diagnosis of Mild Cognitive Impairment (MCI, amnestic single or multiple domain)', 'timeFrame': '48 months'}

Please estimate the sample size based on the assumption: 
The error rate was set at 0.05, and the power was set at 0.80. A power analysis indicated that a sample of 250 participants would be sufficient. An additional 10 participants were added as a safety margin, making the total 260 participants.
Sample size
        The number of participants needed in the study was determined45 on the basis of the anticipated effect size of the ST. Lamont et al
21 conducted a meta-analysis of age-based ST and found an effect size of d=0.52 (95% CI .248 to .717, corresponding to f
2=0.15), when they manipulated ST as we do here. However, as ours is the first study of age-based ST in a clinical setting, we decided to use a lower effect size (f2=0.07) to determine our target sample size, in order to have sufficient power to accurately detect a probably smaller effect in an ecologically valid field experiment. Using this smaller effect size, with the error rate set at 0.05, and power set at 0.80, a power analysis46 indicated that a sample of 250 participants would be sufficient to detect the critical effects of the conditions and their potential interactions with several moderators in a multiple regression analysis (11 predictors: condition, age, physiological stress, 4 vulnerability factors and the interaction terms between condition and these vulnerability factors). We added 10 participants as a safety margin (n=260), in order to ensure that at least 30 participants in each arm meet aMCI criteria for visit 3. Patients will be continuously recruited until the desired sample size is achieved, but not beyond December 2020, to allow sufficient time for the 9-month follow-up before September 2021. Since February 2019, strategies have been implemented to increase recruitment: communication on the AGING protocol has been improved (eg, poster displays in hospitals and general practices, call for participation in AGING on hospital websites) and appointment scheduling and reminders via post, email and/or telephone are being used to retain patients already enrolled in the trial.