Collecting Data - Sample Types

To conduct a pre-election opinion poll on a proposed amendment to the state constitution, a random sample of 10 telephone prefixes- first three digits of the phone number was selected and all households from the phone prefixes selected were called.

• Simple Random Sample

• Stratified Random Sample

• Systematic Sample

• Cluster Sample

• Convenience Sample

Answer explanation

After the selection of the phone prefixes, ALL numbers with those prefixes were selected to be in the sample.

To conduct a study on depression among the elderly, a sample of 30 patients in one nursing home was used.

• Simple Random Sample

• Stratified Random Sample

• Systematic Sample

• Cluster Sample

• Convenience Sample

Answer explanation

Since we are studying the effects of depression on the elderly, it is easiest to look at a nursing home as opposed to a neighborhood / community because we can guarantee that everyone in the nursing home is in fact elderly.

**Students may believe this is Cluster since only ONE nursing home is being used, however, looking at the description, it indicates that a sample of 30 patients were used. Not ALL the patients in ONE elderly home**

To maintain quality control in a brewery, every 20^th bottle of root beer coming off the production line was open and tested.

• Simple Random Sample

• Stratified Random Sample

• Systematic Sample

• Cluster Sample

• Convenience Sample

Answer explanation

Since every 20th bottle (here K=20) is being selected, this is a systematic sample.

Subscribers to the magazine Sound Alive were assigned numbers. Then a sample of 30 subscribers was selected by using a random-number table. The subscribers in the sample were invited to rate new headphones for a “What do Subscribers Think” column.

• Simple Random Sample

• Stratified Random Sample

• Systematic Sample

• Cluster Sample

• Convenience Sample

Answer explanation

Every participant was assigned a number, then a random digit table was used to select the sample. We can also assume that each participant had an equal chance of being selected since there were no additional criteria added to the description (e.g. alphabetical order, order of appearance, what type of subscriber, etc.)

To judge the appeal of a proposed television sitcom, a random sample of 10 people from each of three different age categories was selected and those chosen were asked to rate a pilot show.

• Simple Random Sample

• Stratified Random Sample

• Systematic Sample

• Cluster Sample

• Convenience Sample

Answer explanation

Since participants are randomly selected from each of the three different age categories, this is a stratified random sample with age category as the strata.