When designing your next survey, you’ll face a seemingly simple question that can significantly impact your data quality: Should you use an odd-numbered or even-numbered rating scale? This choice—whether to include that neutral midpoint or force respondents to take a side—has sparked debates among researchers and practitioners for decades.
Let’s explore both perspectives, examine the research, and help you determine which approach works best for your specific survey needs.
Understanding the Fundamental Difference
The core distinction between odd and even rating scales centers on one feature: the midpoint.
Odd-numbered scales (like 1-5 or 1-7) include a middle option that typically represents neutrality, uncertainty, or indifference. The classic 5-point Likert scale, for instance, offers:
- Strongly Disagree
- Disagree
- Neutral (or Neither Agree nor Disagree)
- Agree
- Strongly Agree
Even-numbered scales (like 1-4 or 1-6) eliminate this middle ground, creating what researchers call a “forced choice” design:
- Strongly Disagree
- Disagree
- Agree
- Strongly Agree
This seemingly small design decision can profoundly affect your survey results, response rates, and the actionability of your data.
The Case for Even-Numbered Scales: Forcing Clarity
Proponents of even-numbered scales argue that removing the neutral option produces more decisive, actionable insights.
Benefits of Forced Choice
Eliminates Fence-Sitting
Without a neutral option, respondents must commit to a direction—positive or negative. This prevents what researchers call “satisficing,” where respondents select the middle option as a quick way to complete the survey without careful consideration.
When respondents are provided with forced choice options, they tend to be less willing to provide inaccurate responses by randomly selecting one side, and are more likely to take time to provide accurate and true responses.
Reduces Ambiguity
The neutral midpoint can mean vastly different things to different respondents. Research has shown that people interpret the middle option as representing “no opinion,” “don’t care,” “unsure,” “neutral,” or “it depends”—making it difficult to know what that data point actually represents.
Drives Action
From a business perspective, knowing that a customer is slightly satisfied rather than neutral can be more useful for decision-making. Even-numbered scales have been noted by some practitioners as a way to get unbiased customer feedback, as odd-numbered scales can artificially inflate scores when respondents choose neutral rather than expressing mild dissatisfaction.
When to Use Even-Numbered Scales
Even-numbered scales work particularly well when:
- You’re measuring attributes where true neutrality is unlikely (e.g., satisfaction with a product someone purchased)
- The topic is charged or important enough that people genuinely have opinions
- You need to force prioritization between options
- You’re conducting employee engagement surveys where you need clear directional feedback
- You want to avoid inflated satisfaction scores
The Case for Odd-Numbered Scales: Honoring Neutrality
Advocates for odd-numbered scales argue that genuine neutrality exists and should be captured, not suppressed.
Benefits of Including a Midpoint
Captures Legitimate Neutral Opinions
Not every respondent has a strong opinion on every topic. When a midpoint is absent, respondents who truly feel neutral about the survey topic are forced to choose a negative or positive option, causing incorrect data, or may choose not to respond to the questions, causing missing data.
Improves Response Rates
Forcing people to choose when they genuinely feel neutral can frustrate respondents, leading to survey abandonment or random responses. Some respondents may find forced choice unpleasant and may not complete the survey, particularly for face-to-face surveys dealing with sensitive issues.
Statistical Advantages
Research findings show that scales presenting the neutral category allow for better psychometric characteristics, both in terms of their reliability and with respect to the proportion of accounted variance.
Industry Standards
Many established survey methodologies use odd-numbered scales. The creators of Net Promoter Score (NPS) advocate for a scale of 0-10 rather than 1-10 to include a mathematical midpoint, and the inventors of Customer Effort Score (CES) recommend a 1-7 scale instead of 1-6 or 1-8.
When to Use Odd-Numbered Scales
Odd-numbered scales are particularly appropriate when:
- Measuring attitudes toward topics where neutral positions are valid
- Surveying populations unfamiliar with your topic who may genuinely have no opinion
- Using standardized questionnaires that require comparability over time
- Conducting academic research where capturing the full spectrum of opinions matters
- Following established industry metrics (NPS, CES)
The Midpoint Problem: What “Neutral” Really Means
One of the most compelling arguments against odd-numbered scales is the ambiguity of the midpoint itself.
Research from 2009 showed that interpretations of the mid-point can be quite numerous, with respondents commonly viewing it as meaning no opinion, don’t care, unsure, neutral, equal or both, and neither.
This creates several challenges:
The Dumping Ground Effect
The neutral option can become a catch-all for various sentiments:
- “I don’t understand the question”
- “This doesn’t apply to me”
- “I don’t want to think too hard about this”
- “I genuinely have no preference”
Impact on Data Quality
The choice between odd and even scales can affect completion rates and socially desirable responding, potentially impacting the reliability and validity of results as respondents may switch from one mild directional response to another when the same questions are administered again.
Practical Solutions and Best Practices
Rather than viewing this as an either-or decision, consider these evidence-based strategies:
Strategy 1: Add Separate Options
Instead of relying on the midpoint to capture multiple meanings, provide distinct options:
- Include a “Not Applicable” choice when some questions may not apply to all respondents
- Add an “I don’t know” or “No opinion” option that can be excluded from calculations
- Use an even-numbered scale with optional “Prefer not to answer” outside the scale
By creating a separate category such as undecided, don’t know, or not applicable as appropriate to the survey, respondents aren’t forced to give an opinion in an even-numbered survey and avoid misinterpretation of what a midpoint represents.
Strategy 2: Match Scale to Question Type
For Opinion Questions: Consider even-numbered scales to force directional feedback, as when asking for opinions, there are very few instances where a truly neutral response is valid.
For Fact-Based Questions: The odd versus even distinction matters less, since for fact-related questions where there is no central point, neutral is meaningless.
Strategy 3: Consider Your Research Goals
The decision should be informed by your survey topic, what you know about your respondents, how you plan to administer the survey, and your purpose.
Ask yourself:
- Am I primarily interested in the direction of sentiment or its intensity?
- Will respondents have sufficient knowledge to form opinions?
- Am I tracking trends over time where consistency matters?
- Do I need results comparable to industry benchmarks?
Strategy 4: Scale Length Considerations
Don’t forget that the total number of points matters too:
3-point scales: Quick and simple, but offer limited nuance
5-point scales: The most common, balancing simplicity and discrimination
7-point scales: Provide more granularity for respondents who want to express subtle differences
10-11 point scales: Used in NPS, maximum discrimination but can be cognitively demanding
Research suggests most respondents can meaningfully distinguish between 5-7 options, with diminishing returns beyond that point.
Strategy 5: Improve Question Clarity
Many midpoint issues stem from poorly worded questions. To minimize neutral response problems:
- Make questions specific and concrete rather than vague
- Ensure respondents have the context needed to answer
- Test questions with a small sample before full deployment
- Use clear, balanced language that doesn’t lead respondents
Industry-Specific Considerations
Different industries have developed preferences based on their specific needs:
Customer Satisfaction (CSAT): Commonly uses 5-point scales with a neutral option, though 3-point scales (positive, neutral, negative) are gaining popularity for simplicity.
Employee Engagement: Often employs 5- or 7-point scales with midpoints to capture ambivalence, which can be as important as positive or negative sentiment.
Net Promoter Score (NPS): Standardized at 0-10 (11 points) specifically to include a midpoint at 5.
Customer Effort Score (CES): Typically uses 7-point scales with a neutral midpoint.
Healthcare: Frequently uses even-numbered scales to force patients to indicate whether experiences were more positive or negative than neutral.
Academic Research: Generally prefers odd-numbered scales for comparability and to honor genuine neutral positions.
Testing Your Scale Design
Given the ongoing debate, the best approach is often empirical testing. Consider:
A/B Testing: Run parallel surveys with odd and even versions to compare:
- Response rates
- Distribution of responses
- Completion times
- Quality of open-ended follow-up answers
Pilot Studies: Test your scale with a small sample and ask follow-up questions about:
- How they interpreted the middle option (if present)
- Whether they felt their true opinion was captured
- If any questions felt forced or confusing
Within-Subjects Design: Some researchers use experimental designs where the same respondents are given two parallel forms of scales, one with and one without the mid-point response category, to directly compare psychometric properties.
The Verdict: Context Is King
After examining the research and arguments on both sides, the answer to “odd or even?” is definitively: it depends.
There’s no universally correct answer. The optimal choice depends on:
- Your research objectives
- The nature of your questions
- Your target audience’s familiarity with the topic
- Whether you’re using standardized metrics
- Your tolerance for forced responses versus ambiguous data
Use odd-numbered scales when:
- Following established methodologies (NPS, CES)
- True neutral positions are legitimate and meaningful
- Building longitudinal data requiring consistency
- Respondents may lack knowledge to form opinions
- Academic rigor requires capturing full opinion spectrum
Use even-numbered scales when:
- You need clear directional feedback
- Making business decisions requiring action
- The topic inherently demands an opinion (satisfaction with purchased products)
- You want to prevent satisficing behavior
- Neutral responses would mask slight preferences that matter
Moving Forward with Your Scale Design
As you design your next survey, remember that scale format is just one element of effective survey design. Focus equally on:
Clear Questions: Well-worded questions matter more than scale format.
Appropriate Timing: Send surveys when experiences are fresh in respondents’ minds.
Follow-Up Questions: Pair rating scales with open-ended questions to understand the “why” behind the scores.
Consistency: Once you choose a scale, maintain it across surveys for comparability.
Context-Specific Options: Add “Not Applicable” or “I don’t know” options when appropriate, regardless of whether your scale is odd or even.
The odd versus even debate will likely continue, but by understanding the nuances and trade-offs, you can make informed decisions that serve your specific research needs. Test your assumptions, measure the results, and iterate based on what works best for your organization and your respondents.
